X Atmospheric Refraction and Scattering and Tyndal effect of light related topic-based question answer for CBSE Board Examination
Ans: During sunrise and sunset the sun appears reddish whereas at noon the sun appears white.
Ans: In the visible spectrum, the red color has the largest wavelength. The red colour is least scattered by fog or dust particles. Therefore, we can observe red color easily even in foggy and dusty conditions.
Ans: This is because there is no atmosphere containing air in the outer space to scatter light. Since there is no scattered light, which can reach our eyes in outer space, therefore, the sky looks dark and black there. This is why the astronauts who go to outer space find the sky to be dark and black instead of blue.
4. Is the position of a star as seen by us its true position? Justify your answer.
5. Why do we see a rainbow in the sky only after rainfall?
6. Why is the colour of the clear sky blue?
Ans: Blue colour gets scattered the maximum due to less wave velocity.
During sun rise and sun set, the ray of light coming from the sun get refracted through atmosphere and form apparent position of sun.
Ans. The scattering of light by particles in its path is called Tyndall Effect.
10. The sun near the horizon appears flattened at the sun set and sun rise. Explain why.
Ans: This is due to atmospheric refraction. The density and refractive index of the atmosphere decreases with altitude, so the rays from the top and bottom portion of the sun on horizon are refracted by different degrees. This causes the apparent flattening of the sun. But the rays from the sides of the sun on a horizontal plane are generally refracted by the same amount, so the sun still appears circular along the sides.
CBSE NCERT Physics Class 8 and class 10 chapter light
The change in path of light as it passes through the atmosphere is known as atmospheric refraction. Effects are Blue colour of sky, rainbow in the sky, difference in colours of the Sun observed during sunrise/sunset and noon, sun appears reddish whereas at noon the sun appears white.
1. What is the difference in colours of the Sun observed during sunrise/sunset and noon? Give explanation for each.
Ans: During sunrise and sunset the sun appears reddish whereas at noon the sun appears white.
At sunrise and sunset, the light coming from the sun has to travel a longer distance through the atmosphere to reach us. Therefore, the blue and green components of white light are gets scattered away Hence, during sunrise and sunset the sun appears reddish.
When the sun is overhead at noon, then the light coming from the sun has to travel a relatively shorter distance through the atmosphere to reach us and scattered least. Therefore, all seven colours of sunlight reach to us, Thus, the sun appears white
2. Give reason: Why are the traffic light signals (or danger signals) of red colour?
3. Why does the sky appear dark and black to an astronaut instead of blue?
Ans: No. light from stars undergoes atmospheric refraction which occurs due to the variation in air density.
Ans: We see a rainbow in the sky only after rainfall because the water droplets behave like prisms and disperse sunlight. due to atmospheric refraction and total internal refraction. A rainbow is always formed in a direction opposite to that of the sun.
The water droplets act like small prisms. They refract and disperse the incident sunlight, then refract it internally and finally refract it again when it comes out of the raindrop.
6. Why is the colour of the clear sky blue?
Ans: Blue colour gets scattered the maximum due to less wave velocity.
7. Give reason: What will be colour of the sky in the absence of atmosphere?
Ans: In the absence of any atmosphere, there will be no scattering of sunlight and the sky will appear dark.
8.Why We can see the sun about 2 minutes before the actual sunrise, and about 2 minutes after the actual sunset
Ans: We can see the sun about 2 minutes before the actual sunrise, and about 2 minutes after the actual sunset because of atmospheric refraction. By actual sunrise, we mean the actual crossing of the horizon by the Sun.
Ans: We can see the sun about 2 minutes before the actual sunrise, and about 2 minutes after the actual sunset because of atmospheric refraction. By actual sunrise, we mean the actual crossing of the horizon by the Sun.
During sun rise and sun set, the ray of light coming from the sun get refracted through atmosphere and form apparent position of sun.
Thus ,We can see the sun about 2 minutes before the actual sunrise, and about 2 minutes after the actual sunset.
9. What is Tyndall Effect? Explain with an example.
Ans. The scattering of light by particles in its path is called Tyndall Effect.
When a beam of sunlight enters a dusty room through a window then its path becomes visible to us. This is because the tiny dust particles present in the air of room scatter the beam of light all around the room. And when thus scattered light enters our eyes, we can see the beam of light. Thus, an example of Tyndall effect is the way a beam of sunlight becomes visible as it passes through dust particles in the air of a room.
10. The sun near the horizon appears flattened at the sun set and sun rise. Explain why.
Ans: This is due to atmospheric refraction. The density and refractive index of the atmosphere decreases with altitude, so the rays from the top and bottom portion of the sun on horizon are refracted by different degrees. This causes the apparent flattening of the sun. But the rays from the sides of the sun on a horizontal plane are generally refracted by the same amount, so the sun still appears circular along the sides.
Class 10 physics, Class 10 science Boar exam related Questions
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