Question

Assertion:

Select the correct answer to these questions from the codes (i), (ii), (iii)
and (iv) as given below:


i)Both A and R are true and R is correct explanation of assertion.


ii) Both A and R are true but R is not the correct explanation of the assertion.


iii) A is true but R is false


iv) A is false but R is true.


1. Assertion: when objects are observed through hot air they appear to be moving slightly.

Reason: Hotter air is optically denser and the cooler air is optically rarer.


2. Assertion: The Sun’s disc appears to be flattened at Sunrise and Sunset.

Reason: The Sun is near the horizon at Sunrise and Sunset and Sunlight suffers

atmospheric refraction.​

Answer 1

Answer:

1.i

2.i reason,

Explanation:At sunrise and sunset, the sun is near the horizon. The rays of light from the upper part and lower part of the periphery of the sun bend unequally on travelling through earth's atmosphere. That is why the sun appears oval or flattened at the time of sunrise and sunset.

Answer 2

Atmospheric refraction is the deviation of light from a straight line as it passes through the atmosphere due to the variation in density of the air.

Explanation:

• Because of the refraction of light, objects that are viewed through hot air over a fire appear to move or shake slightly. When the air directly above the fire warms up, it becomes optically rarer than the colder, denser air above it. Hence, the assertion is correct.
• Cold air is denser that hot air that is, hot air is lighter than cold air because molecules of hot air have more heat energy which enables them to expand faster and rise up making it lighter as compared to cold air. Therefore, the reason is incorrect.

Hence, Here (iii) A is True but R is false.

• The rays above and below the sun on the horizon are refracted differently as they go through different layers of atmosphere with different densities. The sun near the horizon at Sunrise and Sunset appears to flatten as a result of this. Hence, the assertion is true.

• Atmospheric refraction causes the sun's disc to appear flatten at sunrise and sunset because The atmosphere's density and refractive index decrease with altitude. Hence, the reason is true and also explains the assertion correctly.

Therefore, Here (i) Both A and R are true and R is correct explanation of assertion.