5.5 More about interference

Question 1

How do wavelength and fringe separation correlate in double slit experiment?

Answer 1

The longer the wavelength of light used, the greater the fringe separation.

Question 2

Which would have greater fringe separation between red and blue light and why?

Answer 2

Fringe separation is greater for red light than for blue light as red light has a longer wavelength than blue light.

Question 3

Define laser

Answer 3

device that produces a parallel coherent be a of monochromatic light

Question 4

Describe the fringe pattern produced by white light

Answer 4

The central fringe is white as every colour contributes at the centre of the pattern.

The inner fringes are tinged with blue on the inner side and red on the outside as red fringes as red fringes are more spaced out than the blue fringes and the 2 fringe patterns don’t overlap exactly.

The outer fringes merge into an indistinct background of white light becoming fainter with increasing distance from the centre as where the fringes merge, difference colours reinforce and hence overlap.