Assertion (A): In case of single slit diffraction intensity of higher order maxima decreases.
Reason (R): Higher order maxima are at larger distance.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is true; the intensity of higher order maxima in single slit diffraction decreases rapidly. Reason (R) is also true; higher order maxima occur at larger distances from the central maximum. However, R is not the correct explanation for A, as the decrease in intensity is due to the smaller effective aperture contributing to these maxima, not their distance.
Assertion (A): On increasing wavelength of light used, resolving power increases.
Reason (R): On increasing wavelength, width of central maxima decreases.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is false. Resolving power of optical instruments (e.g., telescope, microscope) is inversely proportional to the wavelength (\(RP \propto 1/\lambda\)). So, increasing wavelength decreases resolving power. Reason (R) is also false. In diffraction, the width of the central maximum is directly proportional to the wavelength (\(w \propto \lambda\)). Thus, increasing wavelength increases the width of the central maximum.
Assertion (A): In single slit diffraction arrangement, instead of keeping the screen far away, often a converging lens is placed after the slit and a screen is placed at its focus.
Reason (R): Lens doesn’t introduce any extra path difference for a parallel beam.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is true. Using a converging lens to focus the diffraction pattern at its focal plane is standard for Fraunhofer diffraction, simulating far-field conditions. Reason (R) is false. A lens works by introducing varying optical path lengths across its aperture to achieve focusing, thus creating path differences.
Assertion (A): Two persons separated by a \(7\text{ m}\) partition wall in a room of \(10\text{ m}\) high can heard each other easily but cannot see each other.
Reason (R): Any sound wave can bend by the obstacle while light can’t.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true. This is a common observation due to the differing wavelengths of sound and light.
Reason (R) is true. Sound waves have longer wavelengths than light waves, causing them to diffract (bend) significantly around common obstacles. Light waves also diffract, but negligibly so for large obstacles like walls.
Reason (R) correctly explains Assertion (A).
Assertion (A): Diffraction takes place for all types of waves mechanical or non-mechanical, transverse or longitudinal.
Reason (R): Diffraction’s effects are perceptible only if wavelength of wave is comparable to dimensions of diffracting device.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Both Assertion (A) and Reason (R) are true. Diffraction is a universal wave phenomenon, occurring for all wave types. Its effects are most noticeable when the wavelength is comparable to the obstacle's size.
However, (R) states the condition for observation, not the fundamental reason why diffraction occurs for all waves (A).
Assertion (A): Light is diffracted around the edges of obstacles and it bend such a way which is not easily observed.
Reason (R): The wavelength of light is very small.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Diffraction is noticeable when the wavelength is comparable to the obstacle size. Light has a very small wavelength \( approx 400-700 \text{ nm}\), making its diffraction around macroscopic objects hard to observe. Hence, both A and R are true, and R is the correct explanation for A.
Assertion (A): Diffraction is common in sound but not common in light waves.
Reason (R): Wavelength of light wave is more than the wavelength of sound.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Diffraction is pronounced when the wavelength is comparable to the obstacle size. Sound waves have large wavelengths (\( \text{meters}\)), making their diffraction common around everyday objects. Light waves have very small wavelengths (\( \text{nanometers}\)), so their diffraction is less observed. Thus, A is true. The wavelength of light is significantly smaller than the wavelength of sound. Thus, R is false.
Assertion (A): In everyday life, we do not encounter diffraction of light in contrast to that for sound.
Reason (R): Diffraction characteristic is not exhibited by all kind of waves.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true: Observable diffraction occurs when wavelength is comparable to obstacle size. Light's wavelength is very small (nanometers), so its diffraction is not easily observed in daily life, unlike sound (wavelength in meters).
Reason (R) is false: Diffraction is a fundamental property of all waves, although its prominence depends on the wavelength and obstacle size. Hence, (A) is true, (R) is false.
Assertion (A): We cannot get diffraction pattern from a wide slit illuminated by monochromatic light.
Reason (R): In diffraction pattern, all the bright bands are not of the same intensity.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true in a practical sense; a very wide slit (\(a \gg lambda\)) yields a pattern with very small angular spread, making it indiscernible. Reason (R) is true; the intensity of secondary maxima decreases rapidly. (R) does not explain (A).
Assertion (A): Diffraction of light is due to dispersion.
Reason (R): Change in path of light around “the corners separates the wavelength of various colours.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is false; diffraction is the bending of waves, while dispersion is wavelength-dependent refractive index. Reason (R) is false; color separation in diffraction is due to \(\theta \propto \lambda\), not dispersion around corners.