Question

Monochromatic light from a helium-neon laser of wavelength 632.8 nm is incident normally on a pair of parallel slits separated by 0.25 mm.

If the laser is replaced by the microwave transmitter in your experimental setup transmitting 3 cm waves, what slit separation will be needed to maintain the same angle for the first bright fringe?

Give the number only with 2 significant digits after the decimal point, assuming units are in meters.

Answer 1

The first maxima will occur at,

Where D is the distance between the slit and the screen and d is the distance between the slits. Now it is given that the position of the first maxima should be kept constant, and the varying components are the wavelength and the distance between the slits. Hence we can write,

Substituting values we get, (Converting all values to SI Units),

Hence the required distance between the slits is 11.85 m.