14. As we all know, the thermal expansion of aluminum is more significant than that of copper under the same conditions. As shown in Figure 5, a copper-aluminum bimetal is straight at 30℃, so at 60℃, the bimetal will bend to _ _ _ _ _.
15, bimetal is often used for automatic control. As shown in fig. 6, it is a schematic diagram of an incubator. When the circuit is connected, the heating wire heats up and the temperature in the incubator rises. At this time, the bimetal is bent down to _ _ _ _ _ _ _ _ _ _ _, and the circuit is cut off. When the temperature in the box drops, the bimetal will return to its original state and the circuit will be reconnected, so that the temperature in the box can be controlled within a certain range. If the bimetal in the figure is made of copper and aluminum, you should use _ _ _ _ _ _ _ pieces on it.
16, before using the thermometer, you should first observe its _ _ _ _ _ _ _ _, and know its _ _ _ _ _ _ _; When measuring the temperature of a liquid with a thermometer, all _ _ _ _ _ of the thermometer should be immersed in the liquid to be measured.
17. In winter in the north, there will be a thick layer of ice on the lake, as shown in Figure 7. At the junction of the ice surface and the water surface, the water temperature is _ _ _ _ _ _ _ 0℃ (please fill in "greater than", "equal to" and "less than").
On the day of fighting against SARS, one day, after taking his temperature as usual in the morning, Xiao Ming threw away the thermometer, put it on the windowsill and went to school. When I got home at night, I found that the thermometer read _ _ _ _ _℃ (as shown in figure 15). Based on this, he determined that the highest temperature of the day should be _ _ _ _ (select ">" = "
The temperature closest to 23℃ is-().
A. Room temperature that makes people feel warm and comfortable
B. Maximum outdoor temperature in Shanghai in summer
C. Body temperature of healthy adults
D. temperature of ice-water mixture
When Xiaoli measures the temperature of hot water in one beaker, she pours a little hot water into another beaker, as shown in figure 10, and then measures the reading as shown in the figure. When she did this, Xiaoyu found some mistakes, but one of them was problematic. Please pick it out.
A it should not be poured into another beaker, which will lower the temperature.
B. Too little water is poured, and the glass bulb of the thermometer cannot be completely immersed.
C when reading, the line of sight should be flush with the scale line and should not squint.
D, thermometer should be read, should not be read in the water.
10, the following objects under the same conditions, the most obvious volume expansion after heating is-().
A. aluminum block B. copper block
C. Air D. Water
The following is Xiaoyu's knowledge structure listed for some knowledge she has learned. Among them, there is an error ()
Loudness melting
A, the three elements of tone B, the state change that needs to absorb heat is liquefaction.
Timbre sublimation
Good directionality
B, the color of light: the three primary colors of light: red, green and blue D, ultrasonic wave has the characteristics of strong penetration.
The three primary colors of color pigments: red, yellow and blue are easy to obtain concentrated acoustic energy.
7. When the TV is working normally, the back cover will feel a little warm when you try it by hand because some components are hot. It is estimated that the temperature of the back cover is around ().
a 、-20℃ B、 10℃ C、40℃ D、80℃
Compared with ice at 8.0℃ and water at 0℃, it should be ().
A, the ice temperature at 0℃ is low. B, the water temperature at 0℃ is lower.
C, unlike D, has different states of matter and cannot be compared.
9. About melting and solidification, the following statement is true ()
First, the solid has a certain melting point.
B, the crystal should absorb heat when melting, and release heat when solidifying.
The freezing point of the same crystal is lower than its melting point.
D, the crystal will absorb heat when it melts.
10. The melting point of pure iron is 1535℃, and then iron () is 1535℃.
A is solid B, liquid C, and solid-liquid mixed D, all of which are possible.
1 1. Some alloys used in production and life are made by melting different metals. Among several metals listed in the table below, it is difficult to form an alloy with other metals ().
Melting points and boiling points of several metals at standard atmospheric pressure
Metal iron, copper, gold and tungsten
Melting point (℃)1535108310643410
Boiling point (℃) 2750 2595 2707 5627
A, tungsten b, copper c, gold d, iron
12. The following are some examples of physical changes listed by Xiaoli, of which the wrong one is ().
A, the "ice flower" on the window glass in winter is liquefied by the water vapor in the indoor air.
B, we see that the "white gas" of popsicles is a vaporization phenomenon.
C low temperature can be obtained by sublimation of dry ice.
D, there is water on the outer surface of the beverage bottle taken out of the refrigerator, which is liquefied by the water vapor outside the refrigerator.
(a) fill in the blanks
13. The following are six common substances in life: iron, glass, light salt water, mercury, milk and biscuits. Please divide them into two categories: one category includes: the other category includes, which is characterized by.
14. The following four examples describe the "high" of sound, which refers to tone and loudness.
This song is too high for me to sing. Sing loudly
She is a soprano. Please don't "speak loudly"
15. Artificial rainfall is formed by spraying dry ice (solid carbon dioxide) in the air by plane. Dry ice quickly absorbs the heat in the air and becomes the vapor of dry ice, which makes the air temperature drop rapidly. At the same time, the water vapor in the air will turn into small ice particles when it is cold. This is a process, and the ice particles gradually become bigger and fall. In the process of falling, the ice particles become water droplets. This is a process in which water drops fall to form rain.
"Heat pipe" is a device developed in 1980s, with low thermal conductivity. Its thermal conductivity is more than 1000 times that of copper. "Heat pipe" is a kind of metal pipe with closed ends. The inner wall of the pipe is lined with a layer of porous material, which is filled with alcohol or other easily evaporated liquid. When one end of a pipe is heated, the heat will quickly transfer to the other end. What is the reason?
Answer: It turns out that when one end of the pipe is heated, the liquid at this end makes the steam run from the hot end to the cold end. At the cold end, condensation and liquefaction are absorbed by porous materials, and return to the hot end by capillary action, and so on, and heat is sent from the hot end to the cold end.
In order to study the heat absorption ability of objects with different colors, Wang Yong did the following experiments:
Pour water with the same quality and temperature into two identical milk bottles, and wrap the milk bottles with white paper and black paper (as shown in the figure). Then put the two bottles in the sun and measure the water temperature in the bottles every 3 minutes. After half an hour's experiment, the water temperature changes of the two bottles obtained by light rain are shown in the following table.
Sunshine time/min 0 369121518 2124 27 30
White paper bottle water temperature/℃
Water temperature of black paper bottle/℃
1, Wang Yong students "pour water with the same quality and temperature into two identical milk bottles respectively ..." The purpose of satisfying these "sameness" is.
2. After analyzing the above experimental data, we can draw the following conclusions:
Physics examination paper for the eighth grade monthly exam in junior high school (closed book)
(100 minutes out of time 100 minutes)
I. Fill in the blanks (30 points)
1. Fill in the temperature changes of these substances after absorbing heat: 0℃ ice,-4℃ ice.
A substance must be melted from 40℃ to 50℃ ..
As the saying goes, "cold before frost" is because
"Cold after snow" is because
In summer, wrap the glass ball of thermometer with wet cotton and blow it under the electric fan, and the pointer of thermometer will be lowered.
5. Blowing and breathing are gases blown out by the population. Blowing with your mouth in summer makes hot water cool, because it accelerates the temperature of hot water to lower the water temperature, and breathing with your hands warms your hands in winter, mainly because water vapor increases the temperature of your hands when it is cold.
6. When doctors check their teeth in winter, they often put a small mirror on an alcohol lamp and bake it, then put it in their mouth. The purpose of this is:
7. Fill in the appropriate name of the state change in the following blanks:
Artificial rainfall is to spray dry ice in the air by plane. Dry ice quickly absorbs heat in the air and becomes vapor of dry ice, which makes the air temperature drop rapidly. When the water vapor in the air is cold, it becomes small ice particles, and the ice particles gradually become bigger and bigger. In the process of falling, ice particles become water droplets, and water droplets fall to form rain.
8. In daily life, the mirror used by people to correct their appearance makes use of the properties of flat mirror, and the imaging of flat mirror can be explained by light. There is no actual light convergence where the mirror images, so it looks like (fill in "can" or "can't").
9. It is known that the focal length f of the convex lens is 5 cm. (1) When the object distance u = 4cm, you can get _ _ _ _ _ _ _ images; (2) When the object distance u = 12cm, the image can be obtained; (3) When the object distance u = 20cm, an image can be obtained; (4) If you want to get the image of the object on the same side of the lens, the object distance should be in the range of _ _ _ _ _. (Fill in "inverted or upright", "enlarged" or "reduced", "real image" or "virtual image").
10, the calibration part of the commonly used thermometer is a prism, and its front is curved, so that we can see the extremely thin mercury column in the thermometer for reading. This is because the arc acts as a mirror, so that we can see _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
1 1, Xiao Ming conducted an exploratory experiment: put a sounding alarm clock in the bell jar, put a soft foam plastic between the alarm clock and the jar base, and use an air pump to continuously pump out the air in the jar, and the sound of the alarm clock will gradually decrease. This phenomenon shows that sound can spread, but it can't.
12, when the angle between incident light and reflected light is 600, the reflection angle is, and the angle between incident light and mirror surface is. Change the direction of the incident light so that it gradually approaches the normal, and the reflection angle will be _ _ _ _ _ _ _. When it coincides with the normal, the included angle between the reflected light and the incident light will change.
Second, multiple-choice questions (36 points)
1, at standard atmospheric pressure, the melting point of naphthalene is 80℃, so naphthalene is at this temperature ().
A, it must be solid B, it must be liquid.
C, it must be solid-liquid * * * D, and the above three situations are possible.
2. Frozen tofu has holes because ()
A, frozen tofu itself is frozen and shrunk.
B, frozen tofu is formed by self-expansion.
C, make the ice and snow into tofu.
D, the water in the tofu is frozen first, and then melted into water.
3. The following phenomenon is impossible ()
In the cold winter, frozen clothes will dry.
B, wet summer, small water droplets will appear on beer bottles taken out of the refrigerator.
C in windy winter, you will feel cold after swimming.
D. When people who wear glasses walk from indoor to outdoor in winter, small water drops will appear on their glasses.
4. Soak a wet cotton handkerchief in 70% alcohol solution, take it out after it is soaked evenly, unfold the soaked handkerchief, clamp two corners with tweezers, and light it with fire. After the flame on the handkerchief is extinguished, it is found that the handkerchief is intact. The following explanation of this phenomenon is correct ().
This is magic. What you see is illusion.
B, the flame temperature is lower than the ignition point of cotton cloth.
C. The water on the handkerchief vaporizes and absorbs heat, so that the temperature of the handkerchief is lower than the ignition point of cotton cloth.
D, after alcohol combustion, the ignition point of cotton cloth increased.
5. When the pressure cooker with air nozzle is removed from the stove, immediately remove the lid and the soup in the pot ().
A, it will still boil for a while. B, can't cook. C, it may boil. D, it is impossible to judge.
6, put the test tube containing alcohol into a beaker filled with water, and heat the beaker with an alcohol lamp, then the following statement is correct ().
A, alcohol boils before water b, alcohol and water boil at the same time.
C. Water boils before alcohol. D. When the liquid boils, the temperature rises.
7. On a hot summer day, when you are walking on a hot asphalt road, a sprinkler just comes and gets wet. At this time, you will feel more sultry. The main reason for this feeling is ().
A, the water in the shower is exposed to the sun and the temperature is very high.
B, after sprinkling water, the air humidity increases, and the sweat on the body is difficult to evaporate.
C, the water on the ground reflects sunlight, which makes the body gain more heat.
D, after the water evaporates, the tropics on the ground are transferred to people.
8, the following statement is correct ()
A, the endothermic temperature of the object will inevitably rise; B, the exothermic temperature of the object must remain unchanged.
C, the exothermic temperature of the object must be reduced. D, the temperature of the object is constant, must not absorb or release heat.
9. When a photographer processes black and white photos in a darkroom, the liquid column of the thermometer used is blue instead of red. The following statement is incorrect ().
A. The darkroom safety light is red, so the red liquid column of the thermometer is not easy to see in this ring.
The blue liquid column of the thermometer is black under red light.
C. The blue liquid column can be seen more clearly under red light.
D. the red liquid column reflects white light under the irradiation of red light.
10, the following optical instruments or appliances using flat mirror is ()
A. periscope B. car rearview mirror C. solar cooker D. camera lens
1 1. We live in a world of sound. The following sounds: (1) the roar of machines in the factory workshop; (2) The performance of Peking Opera in the theater; (3) Birds singing in the park in the morning; (4) the sound of the electric drill when decorating the house; (5) firecrackers at the wedding; (6) The sound of running water in the mountain stream belongs to noise ()
A.( 1)(3)(4) B.( 1)(2)(5)
C.( 1)(4)(5)d .( 1)(4)(5)(6)
12, the human eye can see an object because it is formed on the retina of the eye.
A. the true image of the real thing. B. The inverted real image magnified by the real object
C. the reduced inverted real image of the physical object D. the enlarged vertical virtual image of the physical object
Three, painting (6 points)
Complete the light path diagram in the figure below.
Fourth, the experimental questions (14 points)
In the experiment of "observing the boiling of water",
(1) The purpose of the experiment is to observe _ _ _ _ _ _ when water is boiling and _ _ _ _ _ _ when water is boiling;
(2) In the experiment shown in Figure (5), the function of using cardboard with holes in the center in the equipment is _ _ _ _ _ _ _ _.
(3) As shown in Figure (6), it is a schematic diagram of bubbles rising when Xiaohua observes the water boiling experiment, where _ _ _ _ _ _ _ _ is the situation when boiling.
(4) The following table is the data recorded by Xiaohua.
Please analyze, the unreliable data is _ _ _ _ _ _ _ _ _, and the measured boiling point of water is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
Time/(minutes) 0 1 2 3 4 5 6 7 8
Temperature (℃)90 92 94 96 96 98 98 98 98 98 98 98 98 98 98
Time/(minutes) 0 1 2 3 4 5 6 7 8
Temperature (℃)90 92 94 96 96 98 98 98 98 98 98 98 98 98 98
Time/Minute 0 1 2 3 4 5 6 7 8
Temperature/℃
V. Calculation and short answer (14)
1. Echo can help ships measure water depth, so sonar is installed on research ships in oceans and rivers. If the propagation speed of sound in water is 1500m/s and the echo is received after 0.8s during the investigation, what is the water depth here?
2. In order to keep warm indoors, residents in northern mountainous areas often stick notes on the window joints, commonly known as "sliding window joints". In order to prevent the paper from falling off due to moisture, it is usually posted outdoors. Please explain why you don't stick a note on the window seam indoors.
The egg just fished out of boiling water is not very hot in your hand. When the water on the surface of the eggshell is dry, it will be very hot. Why?
The eighth grade physics unit detects the name score of the test paper.
1. Multiple choice question: (20×2 = 40, please fill in the answer in the table below)
The title is12345678 910/31415161718 65438.
answer
1. Everything in the world is colorful. About light, the following statement is wrong ()
A. sunlight is composed of various colors of light. Sunlight can be dispersed through a prism.
C. Light is electromagnetic wave D. White light is monochromatic light.
2. In the figure below, the phenomenon of light reflection is ().
3. Common visual defects are myopia and hyperopia. The picture on the right shows the schematic diagram of eyeball imaging for visually impaired people. The type of his vision defect and the type of glasses he needs to wear to correct his vision are ().
A. hyperopia, convex lens B. hyperopia, concave lens
C. myopia, convex lens D. myopia, concave lens
4. Among the following phenomena about light, the correct statement is ()
A. In the sun, the river with a gentle breeze is sparkling, which contains the reflection of light.
B. Turn on the electric light in the cab when the car is driving at night.
C. when looking in the mirror, people always look at the place close to the mirror, because the image formed by the plane mirror will become larger when it is close.
D In a dark room, in order to see your face clearly in the mirror, you should look in the mirror with a flashlight.
LinYu saw a discarded transparent plastic bottle while playing in the forest park. It occurred to her that if it rains, making water in bottles may become the chief culprit of forest fires. So she picked up the bottle and threw it into the trash can. The main cause of the fire is ()
A. A transparent plastic bottle filled with water is equivalent to a convex lens, which can focus light.
B a transparent plastic bottle filled with water is equivalent to a convex lens, which can disperse light.
C a transparent plastic bottle filled with water is equivalent to a concave lens, which can condense light.
D. A transparent plastic bottle filled with water is equivalent to a concave lens, which has a divergent effect on light.
6. The picture is a schematic diagram of an experimental device (the screen is not shown) used to study the imaging law of convex lens. When the candle and lens are placed in the position shown in the figure, an image as large as the object can be obtained on the light screen by moving the light screen. If the lens position remains the same, move the candle to the scale of 30 cm, and then
A. You can get an inverted enlarged image on the screen by moving the light screen.
B. Move the light screen to get an inverted and reduced image on the screen.
C. Move the light screen to get an upright enlarged image on the screen.
D no matter where the screen moves, you can't get a clear image on the screen.
7. As shown in figure 1, OA is the reflection of light from water into the air. If the angle between OA and the water surface is 60? The statements about incident angle α and angle β between refracted light and normal are correct.
A.α=60？ ,β60?
C.α=30？ ,β30?
8. As shown in Figure 2, B is the midpoint of AC. After the candle flame passes through the convex lens, a clear reduced image is formed on the right screen, so the convex lens.
A. it should be somewhere between b and C.
C it should be placed at point b, or it can be placed somewhere to the left of the candle.
9. There are many optical phenomena in daily life and nature, such as: chopsticks inserted into water "bend" on the water surface; The lakeshore scenery forms a reflection in the water; Rainbow after rain; Solar eclipse, lunar eclipse, etc. The reason of the above phenomenon and the corresponding relationship of physical knowledge are incorrect.
A. "Bending" of chopsticks-refraction of light B. Reflection of scenery-imaging by plane mirror
C. Rainbow-light reflection after rain D. Solar eclipse and lunar eclipse-linear propagation of light
10. Among them: ① pinhole imaging, ② flat mirror imaging, ③ magnifying glass imaging, ④ camera imaging and ⑤ slide projector imaging. The following classification is correct ().
A. the real image is 145B. The virtual image is 12344.
C, 23D for reflection imaging and 13④ for refraction imaging.
1 1. The following phenomena are not caused by the straight-line propagation of light ().
A. The formation of hand shadow B. The formation of solar eclipse
C. Formation of solar eclipse D. In the morning, we saw that the sun was still below the horizon.
12. In order to make a beam of parallel light, the students in the class put forward the following methods. Do you think the feasible method is ()?
A. Select a concave lens and place a small light bulb at the focus of the concave lens.
B. Select a convex lens and place a small light bulb on the focus of the convex lens.
C, select a concave lens, and place a small light bulb at twice the focal length of the concave lens.
D. Select a convex lens and place a small light bulb at twice the focal length of the convex lens.
13. In the following light path diagram, the correct one is ().
14. There are six kinds of articles: copper bars, glass fibers, pencil lead, mercury, plastic rods and ceramic pieces. Xiao Ming divides them into two categories, as shown in the following table. Xiao Ming is classified according to what physical properties of ()?
The first and second categories
Copper Rod pencil lead Mercury Glass Fiber Plastic Rod Ceramic Sheet
A. thermal conductivity B. magnetism C. hardness D. conductivity
15. When the medical staff measured the patient's temperature with a thermometer, the mercury in the thermometer remained unchanged during the measurement ().
A, mass b, volume c, position d, temperature
16. Bar code scanners are widely used in business, postal services, transportation and other fields. The main materials of photodiode in scanner are:
A, organic polymer material b, superconducting material c, semiconductor material d, nano material
17. The mass of the following objects is closest to 2kg ().
A. an apple b a rooster c a physics book d a table.
18. Tray balance is a common instrument in scientific experiments. The following statement about its usage is incorrect ()
A. Before weighing an object, the mass of the measured object should be estimated to avoid exceeding the range.
B When weighing, move the code to the right, which is equivalent to adding weight to the plate on the right.
C whether the desktop is horizontal or not, it can be weighed by leveling the beam.
D can't directly weigh chemicals on the pallet.
19. As shown in the figure, the light emitted from point A is directed to point B through the water surface, and the propagation path of light is AOB. If the laser beam points from point B to point A, the incident direction of the laser beam is
A, BC direction, B, BO direction
C, BD direction d, all the above directions are ok.
20. In the cold winter, water pipes often break due to the freezing and expansion of water in the pipes. Because of the () characteristics of foam, sticking foam outside the water pipe can effectively solve this problem.
A. Less hardness B. Good thermal conductivity C. Good thermal insulation D. Good electrical conductivity
2. Fill in the blanks (65438+ 0 for each blank, ***30)
21.At 7: 40 on March 7, 2006, the citizens of Daqing, Heilongjiang Province were surprised to find that there were many "little suns" around the rising sun in Ran Ran, Ran Ran, and a beautiful rainbow appeared above the sun. The main reason for this phenomenon is that there are many small ice crystals hanging vertically in the cloud under special weather conditions (small ice crystals are equivalent to prisms).
(1) The rainbow in the sky shows that sunlight is a kind of (fill in "monochromatic light" or "polychromatic light").
(2) People can see many "small suns" because sunlight is reflected and emitted by small ice crystals, forming _ _ _ _ images. ("Virtual" or "Real")
22. Xiaowen stood 3 meters in front of the vertical plane mirror and saw his own image in the mirror, which was formed by the phenomenon of light. The distance from her image to the mirror is meters; When she approached the mirror at 1m, the distance to her was m.
23. When an aerial photographer shoots a city from high altitude, if the focal length of the camera lens used is 80mm, the distance between the film and the lens should be 80mm (fill in "greater than" or "less than"), and the resulting image will be reduced (fill in "inverted" or "upright") (fill in "real scene" or "virtual scene").
24. According to the latest data from the national survey of students' physical health, the incidence of myopia among primary school students is 22.78%, and that of middle school students is 55.22%. The rapid aging and expanding trend of nearsighted population worries educators and medical workers. Fig. 3 shows the imaging situation of light from an object refracted by the refractive system of hyperopia or myopia and the correction method, in which 1 shows the imaging situation of myopia. The first picture is the practice of correcting myopia. Figure 2 shows the imaging of hyperopia.
25. As shown in Figure 4, where the focal lengths of point P and point F are 2 times and 1 times respectively, the image formed by the object AB through the convex lens may be.
Yes (fill in D.C.B.A), the lens is used to image at point B in life; Use objects to work at point A in life. (Fill in "camera", "slide projector" or "magnifying glass")
26. Use the adjusted pallet balance to measure the quality of the copper block. On the day of the balance, the weights in the right plate are 50g, 20g and 10g, each with 1. As shown in Figure 5, the mass of the copper block is g. If the above experiment is moved to the top of the mountain, the measured mass of the copper block will be (choose "bigger", "unchanged" or "smaller"). If the object is placed on the right disk and the weight is placed on the left disk by mistake, the mass of the measured object is g.
27. Fill in the appropriate units after the following figures:
(1) The mass of a bottle of liquor is about 0.5; (2) The mass of an elephant is about 6000;
(3) The mass of a stamp is about 68.
28.① Copper, ② sugar water, ③ pencil lead, ④ salad oil, ⑤ vinegar, ⑤ glass, ⑤ tap water and ⑧ pure water can be divided into two categories according to their electrical conductivity. One category includes several substances, and their * * * characteristics are as follows; The other category includes several substances with the following characteristics. (Fill in the blanks with serial numbers)
29. Among the four kinds of pencils, ① F, ②HB, ③H and ④B, the order of hardness from strong to weak is: the order of conductivity from strong to weak is: the order of writing color from light to black is. (Fill in the blanks with serial numbers)
30. The screen of the film and the curtain of the teaching projection are made of rough white cloth, because:
(1) The surface roughness is to be formed (fill in "specular reflection" or "diffuse reflection").
(2) White cloth can make people see the true colors.
3. Drawing questions (4 points +2 points +3 points +4 points = 13 points)
The light emitted by the 3 1. luminous point S is reflected by the plane mirror, and two of the reflected light rays are shown in Figure 6. Try to determine the position of the luminous point S and complete the light path diagram. (Drawing in two ways respectively)
32. As shown in Figure 8, it is light reflected by water. Please draw the general direction of the incident light and the refracted light corresponding to the incident light in the picture.
33. Xiaohua saw a frog (pictured) somewhere underwater when he was on a boat tour in Hongze Lake. He irradiated the frog with a laser pen.
(1) Please draw the incident light, refracted light and reflected light when the floret illuminates the frog in the picture;
(2) Is the actual position of the frog deeper or shallower than the "frog" seen by Xiaohua?
A:
34. The light refracted by the convex lens is shown in Figure 4. In Figure 2, the appropriate lens is drawn in the box according to the optical path.
4. Short answer questions and experimental questions (3 points +4 points +5 points +5 points = 17 points)
35. I will give you a convex lens with unknown focal length, a scale and a light bulb on a sunny day. Please tell me how to measure its focal length.
(2) Describe how to make a light source that can emit parallel light and draw its schematic diagram.