Question

Problems HW: Solve the following on grid paper using a compass or circular object to make a decent circle. Scale your diagram properly. DO NOT try to write the answers on this page. They just won't fit. A 4 cm diameter flower is 200 cm from a 50 cm focal length lens of a camera. a) 7. How far should the plane of the camera's light detector be placed behind the lens to record a well-focused image? [65 cm] b) What is the diameter of the image on the detector? [1.3 cm] A stamp collector uses a magnifying lens that sits 2 cm above the stamp. The magnification is 4. What is the focal length of the lens? [2.7 cm]

Answer 1

7a) The lens equation is

do dif

Answer

f 200 50 d -50 66.67cm 200

b) The magnification of the lens is

di 1 do 3 m=

therfore the diameter will also reduce by a factor of 3 thus new diameter = 4/3 = 1.33 cm

Answer: 1.33 cm

c) The magnification is given by

di d do 2

m = 4 therefore d_i = - 8 cm . That is it is formed 8 cm behind the lens in an upright virtual image

The lens equation is

do dif

Answer

dodiーー8 * -= 2.67cm do + di _-8 + 2 = 2.67cm