Answer the following questions:
(a) When a low flying aircraft passes overhead, we sometimes notice a slight shaking of the picture on our TV screen. Suggest a possible explanation.

(b) As you have learnt in the text, the principle of linear superposition of wave displacement is basic to understanding intensity distributions in diffraction and interference patterns. What is the justification of this principle?

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Solution

(a) Weak radar signals sent by a low flying aircraft can interfere with the TV signals received by the antenna. As a result, TV signals may get distorted. Hence, when a low flying aircraft passes overhead, we sometimes notice a slight shaking of the picture on our TV screen.

(b) The principle of linear superposition of wave displacement is essential to our understanding of intensity distributions and interference patterns. This is because superposition follows from the linear character of a differential equation that governs wave motion. If $y_{1} a n d y_{2}$ are the solutions of the second-order wave equation, then any linear combination of $y_{1} a n d y_{2}$ will also be the solution of the wave equation.

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Similar questions

Q. When a low flying aircraft passes overhead, we sometimes notice a slight shaking of the picture on our TV screen .This is because of the direct signal and reflected signal

Q. When a low flying aircraft passes over head, we sometimes notice a slight shaking of the picture on our TV screen. Identify the optical phenomenon behind it.

Q. Assertion :While calculating intensities in interference pattern, we can add the intensities of the individual waves. Reason: Principle of superposition is valid for linear waves.

Q. Assertion :For the situation shown in figure, two identical coherent light sources produce interference pattern on the screen. The intensity of minima nearest to

S_{1}

is not exactly zero. Reason: Minimum intensity is zero, when interfering waves have same intensity at the location of superposition.

Answer the following questions:

(a) In a single slit diffraction experiment, the width of the slit is made double the original width. How does this affect the size and intensity of the central diffraction band?

(b) In what way is diffraction from each slit related to the interference pattern in a double-slit experiment?

(c) When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the shadow of the obstacle. Explain why?

(d) Two students are separated by a 7 m partition wall in a room 10 m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see each other even though they can converse easily.

(e) Ray optics is based on the assumption that light travels in a straight line. Diffraction effects (observed when light propagates through small apertures/slits or around small obstacles) disprove this assumption. Yet the ray optics assumption is so commonly used in understanding location and several other properties of images in optical instruments. What is the justification?

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