Question

A monochromatic beam of laser light falls on a thin slit and produces a series of bright and dark spots on a screen.

 

If this apparatus (slit and screen) is submerged in water, the dark spots

will not change their location on the screen

will move away from the center spot

will move toward the center spot

Answer 1

From y/L = m(wavelength)/a we can start

When you immerse the apparatus in water we have to apply n(wavelength) water = n(wwavelength)air

or wavelength water = wavelength air/nwater

Thus, the wavelength in the water will be decreased

If you decrease the wavelength, the value of y decreases. That means the dark spots are moving closer to the center.