Question

Assertion : Power of a convex lens is positive
and that of a concave lens is negative.
Reason : Convex lens forms real image and
concave lens forms virtual image.
(a) Both Assertion and Reason are true
and Reason is the correct explanation
of Assertion.
(b) Both Assertion and Reason are
true but Reason is not the correct
explanation of Assertion.
(c) Assertion is true but Reason is false.
(d) Both Assertion and Reason are false

Answer 1

Assertion(A): Power of a convex lens is positive and that of a concave lens is negative.

Reason(R) : Convex lens can form real image and concave lens forms virtual image only.

Assertion is correct but Reason is False.

But why?

Focal length of a convex lens is positive, hence the power of a convex lens is also positive.

Similarly, cal length of a concave lens is negative, hence the power of a concave lens is also negative.

So, Assertion is true .

But, regarding image formation :

Concave lens form virtual images only.

But , convex lens can produce both virtual and real images depending upon the position of the object.

So, Reason is false.

PLS MARK ME AS BTRAINLIST

Hope It Helps.

Answer 2

(c) Assertion is true but Reason is false.

• A positive focal length gives a convex lens its power, whereas a negative focal length gives a concave lens its power. Hence, convex lens and concave lens have positive and negative powers respectively.
• Depending on the position of the object in front of the lens, a convex lens can produce both real as well as virtual images whereas a concave lens only forms virtual images. So, the reason is not completely correct.
• Therefore, Assertion is true but Reason is false.