JEE Main · 2021 · 24 Feb 2021 · Shift 1 · Geometrical Optics

The focal length

f

is related to the radius of curvature

r

of the spherical convex mirror by:

(A) $f = r$
(B) $f = - \frac{1}{2} r$
(C) $f = - r$
(D) $f = + \frac{1}{2} r$ ✓ Correct

Answer: (D)

Solution

For a spherical convex mirror, the focus and center of curvature are on the same side (behind the mirror).

By the mirror formula convention, both focal length and radius of curvature are positive for a convex mirror.

The relationship is:

f = + \frac{r}{2}

JEE Main · 2021 · 24 Feb 2021 · Shift 1 · Single correct option

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