NIOS Class 12 Physics Chapter 22 Wave Phenomena and Light

NIOS Class 12 Physics Chapter 22 Wave Phenomena and Light Solutions English Medium As Per New Syllabus to each chapter is provided in the list so that you can easily browse throughout different chapters NIOS Class 12 Physics Chapter 22 Wave Phenomena and Light Notes in English and select need one. NIOS Class 12 Physics Solutions English Medium Download PDF. NIOS Study Material of Class 12 Physics Notes Paper Code: 312.

NIOS Class 12 Physics Chapter 22 Wave Phenomena and Light

Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Physics Notes, NIOS Senior Secondary Course Physics Solutions in English for All Chapter, You can practice these here.

Wave Phenomena and Light

Chapter: 22

Module – VI: Optics And Optical Instruments

INTEXT QUESTIONS 22.1 

1. What is the relative orientation of a wavefront and the direction of propagation of the wave?

Ans: The wavefront is always perpendicular to the direction of propagation of the wave. In other words, if a light wave is traveling in a particular direction, the wavefront at any instant is a surface where all the points are in the same phase, and this surface is oriented at right angles to the travel path of the wave. This means the light ray, representing direction of energy, always points at 90° to the wavefront.

(i) For a spherical wavefront, the rays (direction of propagation) are radial, extending outward from the source.

(ii) For a plane wavefront (as from a distant source), the rays are parallel and perpendicular to the flat wavefront.

2. A source of secondary disturbance is emitting wavelets at an instant t = 0 s. Calculate the ratio of the radii of wavelets at t = 3s and t = 6s.

Ans: Given: t₁ = 3s

t₂ = 6s

The radius (r) of a wavelet = speed of wave (v) × time (t). So,

At t₁, r₁ = v × 3

At t₂, r₂ = v × 6

Ratio of radii = r₁ : r₂ 

= (v × 3) : (v × 6) 

= 3:6

= 1:2

Hence, the radius at 6s is twice that at 3s.

INTEXT QUESTIONS 22.2 

1. On what factors does the resultant displacement at any point in the region of superposition of two waves depend?

Ans: The resultant displacement at any point where two waves superpose depends mainly on:

(i) The amplitude of each wave.

(ii) The phase difference between the two waves at that point.

If both waves have the same frequency and amplitude, the relative phase (how much one is shifted relative to the other) determines whether their sum at that point is constructive (larger displacement) or destructive (smaller or zero displacement).

2. In Young’s experiment, how is the constructive interference produced on the screen?

Ans: Constructive interference on the Young’s double-slit screen occurs when waves from the two coherent sources arrive at a point in phase. That is, the path difference between the two waves must be an integer multiple of wavelength (nλ, where n = 0, 1, 2, …).

(i) At these points, the crests of one wave align with the crests of the other, and the resulting amplitude is maximum.

(ii) These spots appear as bright fringes on the screen.

3. If we replace the pinholes S₁ and S₂ by two incandescent light bulbs, can we still observe the bright and dark fringes on the screen?

Ans: No, we cannot observe the bright and dark fringes if S₁ and S₂ are replaced by two separate bulbs. Incandescent bulbs act as incoherent sources: their light waves have random phase relationships, different frequencies, and amplitudes. Interference patterns require coherent sources, where the phase difference remains constant. With incoherent sources, the screen shows uniform illumination (no fringes).

4. What are coherent sources? Can our eyes not act as coherent sources?

Ans: Coherent sources are those that emit waves of:

(i) The same frequency.

(ii) The same wavelength and amplitude.

(iii) A constant phase difference between them.

Our eyes cannot act as coherent sources, because they do not emit light of fixed phase relationship. The light waves from our eyes are not regular, and do not maintain the same frequency, amplitude, or phase with respect to one another.