interference practice questions

In Newton's ring experiment, predict, what will happen if a few drops of a transparent liquid introduced between the lens and plate?

• The diameters of fringes contracted.

• The diameters of fringes remain same.

• The diameters of fringes increased.

Why the colors of thin films in reflected and transmitted light are complimentry?

• Due to additional path difference of

  $\frac{\lambda}{2}$ in reflected rays

• Due to additional path difference of $\frac{\lambda}{2}$ in transmitted rays

• No additional path difference in reflected rays

If Young's apparatus is immersed in water, the effect on the fringe width will

• Remain same

• Decrease

• Increase

• Can't say

If the angle

 $\alpha$  of the biprism is increased, then 

• The distance between two virtual sources would increase.

• Fringe width is decreased 

• The distance between two virtual sources would increase and the fringe width is decreased 

• None f these

In Newton's ring experiment, if the monochromatic source of light is replaced by another monochromatic source of higher wavelength, what will be the affect on the radius of the rings.

• The radius will Increase.

• The radius will decrease.

• The radius will same.

• There is uniform illumination.

In the young's double slit experiment, the distance between the slits is 0.2 mm and screen is at a distance 1 m. The third bright fringe is at a distance 7.5 mm from the central fringe. Find the wavelength of light used.

• 5500Å

• 6000Å

• 5000Å

• 4500Å

In the Young's double slit experiment, the angular width of fringe formed on a distant screen is 0.1⁰. The wavelength of light used is 4000 Å. Find the spacing between the slits?

• 0.345 mm

• 0.230 mm

• 0.435 mm

• 0.320 mm

Light of wavelength 6000 Å falls normally on a wedge shaped film of the refractive index 1.4 forming fringes that are 2 mm apart. Find the angle of the wedge in radian.

• 1.071 x 10^-4 radian

• 2.071 x 10^-4 radian

• 1.71 x 10^-4 radian

• 1.5 x 10^-4 radian

In reflected light system, at the edge of wedge, the thickness of film is zero, hence it satisfies the minima condition for n=0. Therefore, at the point of contact the fringe will be dark.

• False

• True

The conditions for sustained interference are

• The two sources must be monochromatic and coherent.

• The two sources must be monochromatic, but not coherent.

• The two sources must be coherent, but not monochromatic.

• The background should be dark.