Science (English Medium) Class 12 - CBSE Important Questions

"If the slits in Young's double slit experiment are identical, then intensity at any point on the screen may vary between zero and four times to the intensity due to single slit".

Justify the above statement through a relevant mathematical expression.

Draw the intensity distribution as function of phase angle when diffraction of light takes place through coherently illuminated single slit.

In a Young’s double slit experiment, the path difference at a certain point on the screen between two interfering waves is `1/8`th of the wavelength. The ratio of intensity at this point to that at the centre of a bright fringe is close to ______.

ASSERTION (A): In an interference pattern observed in Young's double slit experiment, if the separation (d) between coherent sources as well as the distance (D) of the screen from the coherent sources both are reduced to 1/3^rd, then new fringe width remains the same.

REASON (R): Fringe width is proportional to (d/D).

Assertion(A): The photoelectrons produced by a monochromatic light beam incident on a metal surface have a spread in their kinetic energies.

Reason(R): The energy of electrons emitted from inside the metal surface, is lost in collision with the other atoms in the metal.

A narrow slit is illuminated by a parallel beam of monochromatic light of wavelength λ equal to 6000 Å and the angular width of the central maximum in the resulting diffraction pattern is measured. When the slit is next illuminated by light of wavelength λ’, the angular width decreases by 30%. Calculate the value of the wavelength λ’.

Draw the graph showing intensity distribution of fringes with phase angle due to diffraction through a single slit. What is the width of the central maximum in comparison to that of a secondary maximum?

How will the interference pattern in Young's double-slit experiment be affected if the screen is moved away from the plane of the slits?

How will the interference pattern in Young's double-slit experiment be affected if the source slit is moved away from the plane of the slits?

How will the interference pattern in Young's double-slit experiment be affected if the phase difference between the light waves emanating from the two slits S₁ and S₂ changes from 0 to π and remains constant?

Monochromatic light of wavelength 600 nm is incident from the air on a water surface. The refractive index of water is 1.33. Find the

1. wavelength,
2. frequency and
3. speed, of reflected and refracted light.

A beam of light consisting of two wavelengths 600 nm and 500 nm is used in Young's double slit experiment. The silt separation is 1.0 mm and the screen is kept 0.60 m away from the plane of the slits. Calculate:

1. the distance of the second bright fringe from the central maximum for wavelength 500 nm, and
2. the least distance from the central maximum where the bright fringes due to both wavelengths coincide.

A ray of light of wavelength 600 nm propagates from air into a medium. If its wavelength in the medium becomes 400 nm, the refractive index of the medium is ______.

In Young's double-slit experiment, the separation between the two slits is d and the distance of the screen from the slits is 1000 d. If the first minima fall at a distance d from the central maximum, obtain the relation between d and λ.

A ray of light travels a distance of 12.0 m in a transparent sheet in 60 ns. The refractive index of the sheet is ______.

In an interference experiment, a third bright fringe is obtained at a point on the screen with a light of 700 nm. What should be the wavelength of the light source in order to obtain the fifth bright fringe at the same point?

How is a wavefront different from a ray?

Using Huygens’s construction of secondary wavelets draw a diagram showing the passage of a plane wavefront from a denser to a rarer medium. Using it verifies Snell’s law.

Sketch the graphs showing variation of stopping potential with frequency of incident radiations for two photosensitive materials A and B having threshold frequencies v_A > v_B.

(i) In which case is the stopping potential more and why?

(ii) Does the slope of the graph depend on the nature of the material used? Explain.

Calculate the wavelength of radiation emitted when electron in a hydrogen atom jumps from n = `oo` to n = 1.