Question

An object in front of a concave mirror has a real image that is 11.5 cm from the mirror. The mirror's radius of curvature is 14.0 cm. (Include the sign of the value in your answers.)

(a) What is the object distance?

(b) What is the magnification?

Answer 1

Solution) di = + 11.5 cm ( real image )

R = 14 cm

R = 2f

f = (R/2)

f = (14/2) = 7 cm

f = + 7 cm ( concave mirror )

(a) Object distance , do = ?

(1/f) = (1/do) + (1/di)

(1/do) = (1/f) - (1/di)

(1/do) = (1/7) - (1/11.5)

(1/do) = ( 11.5 - 7 )/(11.5×7)

do = (11.5×7)/(4.5)

do = 17.8 cm

(a) Therefore object distance , do = + 17.8 cm

(b) Magnification , m = ?

m = - (di/do)

m = - (11.5/17.8)

m = - (0.646)

m = - 0.646