Question

An object 6 centimeters high is placed 30 centimeters from a concave mirror of focal length 10 centimeters as shown above.

(a) On the diagram above, locate the image by tracing two rays that begin at point P and pass through the focal point F. Is the image real or virtual? Is it located to the left or to the right of the mirror?

(b) Calculate the position of the image.

(c) Calculate the size of the image.

(d) Indicate on the diagram above how the ray from point P to point Q is reflected, if aberrations are negligible.

Answer 1

(a)

(b) 1/f = 1/d_o + 1/d_i … 1/10 = 1/20 + 1/ d_i … d_i = 15 cm

(c) M = – d_i / d_o … M = –15/30 = –0.5 … M = h_i / h_o … –0.5 = h_i / 6cm … h_i = – 3cm

(d) Reflection Ray PQ is shown in the diagram as the topmost ray. For this ray, the incoming θ = reflection θ.