Question

Chromatic aberration comes from the fact that different wavelengths of light travel at different speeds through the material of the lens; that is, they have different indices of refraction, a property known as dispersion. This means that a lens, in effect, has different focal lengths for different wavelengths of light. Consider a lens made to the following specifications: focal length for red light fred=19.57cm, focal length for blue light fblue=18.87cm.

Part A

Consider an object 5.000cm tall placed a distance 30.00cm from the lens. Assuming that the object reflects both red and blue light, find the ratio yredyblueof the height of the red image to the height of the blue image.

Express your answer numerically to three significant figures.

Answer 1

For red light

=> 1/v = 1/19.57 - 1/30

=> v = 56.3 cm

=> height of image = 5 * (56.3/30)

                                    =   - 9.38 cm

For blue light

=> 1/v = 1/18.87 - 1/30

=> v = 50.86 cm

=> height of image = 5 * (50.86/30)

                                    =   - 8.477 cm

=> ratio the height of the red image to the height of the blue image = 9.38/8.477

                                                                                                          = 1.106