A plano convex lens of ( f = 20 c m ) is silvered at plane surface. New f will be

Question

A plano convex lens of ( f = 20 c m ) is silvered at plane surface. New f will be, 20 cm, 40 cm, 30 cm, 10 cm

MARKS App · Accepted Answer

As 1 f = ( μ - 1 ) 1 R 1 - 1 R 2 ∴ 1 20 = ( 1.5 - 1 ) 1 ∞ - 1 R 1 20 = - 1 2 R , R = - 10 cm Refraction from rarer to denser medium - μ 1 u + μ 2 v = μ 2 - μ 1 R , where u = ∞ , v = f ∴ 0 + 1.5 f = 1.5 - 1 10 = 1 20 , f = 30 c m

Search any question & find its solution

Looking for more such questions to practice?