Chapter 9: ray optics and optical instruments Assertion Reason
These questions of two statements each, printed as Assertion and Reason. While answering these Questions you are required to choose any one of the following four responses.
(A) If both Assertion & Reason are true & the Reason is a correct explanation of the Assertion.
(B) If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.
(C) If Assertion is true but the Reason is false.
(D) If Assertion & Reason both are false.
Q.1 Assertion : Diffraction takes place for all types of waves mechanical or non-mechanical, transverse or longitudinal.
Reason : Diffraction’s effects are perceptible only if wavelength of wave is comparable to dimensions of diffracting device.
(1) A (2) B (3) C (4) D
Answer: 2
Q.2 Assertion : In Fraunhofer diffraction central observation point is always bright where as in fresnel diffraction observation point may bright or dark.
Reason : In fresnel light waves approaches at observation point are always in same phase, whereas in Fraunhofer light waves approaches at central observation point may be in same phase or in opposite phase.
(1) A (2) B (3) C (4) D
Answer:3
Q.3 Assertion : Diffraction of sound waves are more easily observed as compare to light waves.
Reason : Wavelength of sound waves is more as compare to light.
(1) A (2) B (3) C (4) D
Answer:1
Q.4 Assertion : If distance between aperture and screen decreases continuously, then observation point becomes bright and dark in alternate order.
Reason : When even HPZ passess from the aperature then observation point becomes bright and when odd HPZ passess from the aperature then this point becomes dark.
(1) A (2) B (3) C (4) D
Answer:3
Q.5 Assertion : In the diffraction pattern of small circular disc, as the size of disc increases, brightness at the centre of its geometrical shadow decreases.
Reason : According to fresnel’s theory, resultant amplitude at centre is ± . If n increases then Rn+1 decreases.
(1) A (2) B (3) C (4) D
Answer:1
Q.6 Assertion : Waves emitted from alternate HPZ are in same phase.
Reason : Path difference of waves emitted from successive HPZ and approaching at observation point is l/2.
(1) A (2) B (3) C (4) D
Answer:1
Q.7 Assertion : Resultant intensity at observation point due to complete wavefront is , where I0 is the intensity due to first HPZ.
Reason : If n is too high then resultant amplitude at observation point is .
(1) A (2) B (3) C (4) D
Answer:1
Q.8 Assertion : When more number of odd HPZ allow from the aperature, then intensity at observation point continuously decreases.
Reason : Amplitude of higher order HPZ is more than amplitude of lower order HPZ
(1) A (2) B (3) C (4) D
Answer:3
Q.9 Statement I : Light waves can be polarised.
Statement II: It is because light waves are transverse in nature.
Answer:
Q.10 Statement I : Diffraction of sound waves is difficult to observe then diffraction of light waves.
Statement II: Wavelength of light is very small as compared to the wavelength of sound.
Answer:
Q.11 The angle of incidence at which reflected light in totally polarized for reflection from air to glass(refractive index n), is –
(A) sin–1 (n) (B) sin–1 (1/n)
(C) tan–1 (1/n) (D) tan–1 (n)
Answer:
Q.12 When an unpolarized light of intensity I0 is incident on a polarizing sheet, the intensity of the light which does not get transmitted is –
(A) I0 (B) I0 (C) zero (D) I0
Answer:
Chapter 7: Alternating Current Assertion Reason
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Class 12 Physics Notes
