Physics problems with answers in the second day of junior high school

1. Some people have the following understandings of sound phenomena, of which the correct one is ().

A. the speed of sound is constant in all kinds of media. Sound travels at maximum speed in a vacuum.

C. air is the medium of sound. People speak by vibrating their tongues.

2. The following statement is true ()

A. The formation of "shadow" shows that light travels in a straight line in the same medium.

B. The closer a person is to a flat mirror, the bigger the image becomes.

C. the propagation speed of light in a vacuum is

D. diffuse reflection will occur when light shines on clothes.

3. The following statement about light phenomenon is correct ()

A. Both solar and lunar eclipses are caused by the linear propagation of light.

Plane mirror imaging is caused by the refraction of light.

C. The small fish in the water and the white clouds in the blue sky seen in the lake are all virtual images formed by the reflection of light.

D People see objects that do not emit light because the diffuse reflection on the surface of the object does not obey the law of light reflection.

Among the 24 solar terms, the sun shines vertically on the tropic of Capricorn only during the winter solstice. At noon from the winter solstice, if a straight pole with a length of 1m is vertically erected on the horizontal line in Beijing, its shadow should be (the latitude of Beijing is 40 north latitude, and the latitude of Capricorn is 23.5 south latitude, which is a right triangle with an acute angle of 63.5).

A.0.5m B. 1m C. 2m D. 2.5m

5. "When we meet in Gusu, everyone sleeps in the river." People standing on the shore can see the reflection of Gusu people through the calm water. It reflects ().

A. Virtual image formed by light reflection B. Virtual image formed by light refraction

C. Real image formed by light reflection D. Real image formed by light refraction

6. About the spread of sound, the following statement is wrong ()

A. sound travels in one direction along a straight line.

B. When the sound encounters a big obstacle, it will reflect and form an echo.

C. When the sound encounters small obstacles in the propagation process, it can be bypassed.

Sound travels at different speeds in different media.

7. As shown in figure-1, the three rays of light A, B and C converge at point P. If a plane mirror is arbitrarily placed in front of point P, then ().

The three reflected rays may or may not intersect at a point.

B. Three reflected rays cannot intersect at one point.

C. three reflected rays must intersect at one point.

D the extension lines of the three reflected rays intersect at a point behind the mirror.

8. The following statement about light phenomenon is true ()

A. When light diffuses, it does not obey the law of light reflection.

B. When the light obliquely enters the water from the air, the refraction angle is greater than the incident angle.

C after sunlight enters the earth's atmosphere, its propagation path may be bent.

D. The flat mirror can image, and it is an enlarged virtual image.

9. When studying the experiment of convex lens imaging, it is found that when the distance from the object to the convex lens is 5cm, the convex lens becomes an upright image; When the distance from the object to the convex lens is 8cm, it becomes an inverted image. The following statement is true ()

A. When the distance from the object to the convex lens is 3cm, it becomes an enlarged real image.

B. When the distance from the object to the convex lens is 10cm, it becomes an enlarged real image.

C. When the distance from the object to the convex lens is 13cm, it must be an inverted and reduced real image.

D. When the distance from the object to the convex lens is 17cm, it must be an inverted and reduced virtual image.

10. When a bee flies with nectar, its wings vibrate 300 times per second on average, and when it does not carry nectar, it vibrates 440 times per second on average. Experienced beekeepers can tell whether bees fly out to pick flowers or fly home with honey. Beekeepers mainly distinguish other things according to what characteristics ().

A. the tones of sounds are different. B. The loudness of the sound is different

C. Different flight path shapes D. Different flight heights

Second, fill in the blanks

1 1. As shown in the figure, -2 is a parallel beam from two endpoints of the sun to the moon. When observing a solar eclipse, different observers can observe it at points A, B, C, D and E on the earth's surface or at points F, G, H, I and J in the outer space of the earth. In the above 10 region, a total solar eclipse can be observed. It can be observed that the position of annular eclipse is _ _ _ _ _ _ _ _ _ _ _ _; It can be observed that the position of the partial solar eclipse is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

12. When pouring water into a thermos bottle, the sound tone becomes more and more _ _ _ _ _. This sound is produced by the _ _ _ _ _ _ _ vibration in the bottle.

13. Open your eyes, stretch out your right hand, cover your eyes with four fingers together and look at the sun. You will see a piece of red in front of you, indicating that red blood can be transmitted or reflected _ _ _ _ _ _ _ _ _.

14. Solar eclipses usually occur around _ _ _ _ _ _ of the lunar calendar.

15. "The monkey fished for the moon with a sieve." When the monkey fished for the moon, waves were generated on the water. At this time, the moonlight reflected on the water, and the moon in the water disappeared.

16. Among seven kinds of visible light, namely red, orange, yellow, green, blue, indigo and purple, the color light with the shortest wavelength is _ _ _ _ _ _ and the color light with the longest wavelength is _ _ _ _ _ _.

17. The "sight distance" of normal eyes is _ _ _ _ _ cm. Xiaohong wants to carefully observe the skin on her face through the mirror, so the most suitable distance between the small mirror and her eyes should be around _ _ _ _ _ _ _ cm (Xiaohong has normal vision).

18. In the evening, some students fell asleep, and the karaoke bars outside the school were still open, and some students were awakened by singing. A classmate got up and closed the window. Student b simply covered her head with a quilt and fell asleep. C students go to karaoke bars and ask to turn down the volume. The method they adopt to reduce noise is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

19. As shown in Figure -3, standing on a high place like this and calling to the distance, its purpose is _ _ _ _ _ _ _ _.

20. As shown in Figure -4, a person seems to have a fish at point A. If you want to illuminate the fish in the water at point A with the light of a flashlight, the light of the flashlight should be aimed at _ _ _ _ _ _ _ _. (Fill in B, C, E and D first)

Third, experimental inquiry questions.

2 1. zhong -5, can you explain their acoustic principles?

Fourth, drawing questions.

22. As shown in Figure -6, a beam of light AB emitted by point power supply S hits the mirror MN, and CD is the reflection of another incident light emitted by S. Please draw the position of point power supply S in the figure.

23. In Figure -7, MN is the optical axis of the lens and the image of AB. Draw the lens in the appropriate position in the picture and find out the position of the focus.

24. As shown in Figure -8, placing concave lens A in front of convex lens B at 10cm can make a beam of light parallel to the main optical axis pass through two lenses and converge on the screen S of Nie convex lens at 15cm. If the concave lens is removed and the position of the convex lens and the screen remains unchanged, then a point light source C can be placed on the convex lens axis 30cm away from the convex lens, so that the point C can also be imaged on the screen.

Try to make the focal point f of concave lens and find its focal length F.

Fifth, the calculation problem.

25. As shown in Figure -9, a beam of light obliquely downward at an angle of 45 degrees with the ground is blocked by one side of a pair of parallel plane mirrors and reflected to the ground many times. Given that the incident point is h from the ground and the distance between mirrors is a, what is the total optical path after being repeatedly reflected by the mirrors? What is the number of reflections?

In 2006, the new curriculum standard people's education edition last semester eighth grade physics examination paper.

Reference answer

One,

1.C

2.D

3.A

4.C

5.A

6.A

7.C

8.C

9.B

10.A

Second,

1 1.h； c； b、D、G、I

12. High air column

red

14. Grade one

15. Diffuse reflection

16. Purple

17.25; 12.5

18. block noise propagation; Weakening in the human ear; Weaken from the sound source

19. Concentrated sound waves travel far.

20.b (according to the reversibility of light)

Third,

Figure 2 1. A means that the sounding object is vibrating (or the sound is generated by the vibration of the object). Figure B shows that the vibration of the steel ruler can make a sound (or the sound is related to the vibration speed of the object). Figure c shows the reason of echo location.

Figure A -30

The incident light SC of CD passes through AB at S, then S is the position of point light source.

23. as shown in figure A -3 1

(1) connecting MN to O, where O is the center of the convex lens; ② When the incident light parallel to the main optical axis intersects with the convex lens, A crosses to C, and C connects to MN to F, where F is the focus of the convex lens.

Figure A -32

25.① ②