Question

Assertion : Intensity of image formed by a spherical mirror of small aperture is more.
Reason: Intensity < (Aperture)square
(1) Both A and R are true and R is correct explanation of the assertion.
(2) Both A and R are true but R is not the correct explanation of the assertion.
(3) A is true but R is false.
(4) A is false but R is true.​

Answer 1

Answer:

3

Step-by-step explanation:

the square of intensity of the image formed by a spherical mirror is directly proportional to the area of the aperture

Answer 2

Answer:

(3) A is false but R is true is the Correct Answer. This means assertion is wrong but the reason is a true statement.

Step-by-step explanation:

When we talk of spherical mirrors, we take several concepts into account like Aperture, Focal Length, Diameter of Aperture, Curvature, etc.

Now, Intensity means brightness of the image we obtained i.e., how bright it is. It depends on Diameter of Aperture, which is the distance of one end of mirror to the other end of mirror.

Now, according to formula for intensity, intensity is directly proportional to the area of aperture.

Therefore, I∝A

where, A is area of aperture.

Now A = πr²

where, r is radius of aperture.

we know, r = d/2

where, d is diameter of aperture. Hence, putting this value in the above equation:

A = π(d/2)²

   = (πd²)/4  

This gives us the relation as I∝d² .

This concludes, Intensity being directly proportional to diameter of aperture's square. It means small aperture indicates less intensity. Hence, assertion is wrong.

Now, as intensity∝(diameter of aperture)²

Hence, reason statement is correct.