Optics Question 16
Assertion : The illumination of earth’s surface from sun is more at noon than in the morning. Reason : Luminance of a surface refers to the luminous flux per unit area.
Options:
A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but reason is not the correct explanation of the assertion.
C) If assertion is true but reason is false.
D) If the assertion and reason are both false.
E) If assertion is false but reason is true.
Show Answer
Answer:
Correct Answer: B
Solution:
At noon, rays of sunlight fall normally on Earth.
Therefore q = 0°. According to Lambert’s cosine law, $ E\propto \cos \theta , $ when q = 0°, cos q = cos 0° = 1 = max.
Therefore, E is at its maximum.
BETA
