JEE Main Physics - Wave Optics
Exam Duration: 60 Mins Total Questions : 30
Ray optics is valid, when characteristic dimensions are
- (a)
much smaller than the wavelength of light
- (b)
much larger than the wavelength of light
- (c)
of the same order as the wavelength of light
- (d)
of the order of one millimetre
In the young's double slit experiment, the two slits \({S}_{1}\)and \({S}_{2}\)are not equidistant from the monochromatic light source slit S which is illuminating them.Then, the central fringe is
- (a)
always bright
- (b)
always dark
- (c)
uniformly illuminated
- (d)
either dark or bright depending on the position of S.
Two sources of light are said to be coherent if the waves produced by them have the same
- (a)
frequency and amplitude
- (b)
amplitude and phase
- (c)
phase and amplitude
- (d)
phase and wavelength
To demonstrate the phenomenon of interference, we require
- (a)
two sources which emit radiations of same frequency
- (b)
two sources which emit radiations of nearly same frequency
- (c)
two sources which emit radiations of same frequency and have a definite phase relationship
- (d)
two sources which emit radiations of different wavelengths
Interference was observed in interference chamber where air was present, now the chamber is evacuted, and if the same light is used, a careful observe will see
- (a)
No interference
- (b)
interference with brighter bands
- (c)
interference with dark bands
- (d)
interference fringes with larger width
In young's double slit experiment, light of wavelength 600 mm gives 40 bright and dark fringes.If the given light is replaced by light of wavelength 400nm how many fringes will be seen?
- (a)
30
- (b)
40
- (c)
50
- (d)
60
What happens to the pattern in young's experiment when the monochromatic source is replaced by the white-light source?
- (a)
All bright fringes become white
- (b)
No fringes are observed
- (c)
All bright fringes get coloured from violet to red
- (d)
Only the central fringe is achromatic, all other fringes are coloured
In a double slit arrangement mono-chromatic light gives fringes on a screen.If the screen is moved by \(5\times { 10 }^{ -2 }\)m towards the slits,the change in fringe width is \(3\times { 10 }^{ -5 }\)m.If the distance between the slits is \({ 10 }^{ -3 }\)m, what is the wavelength of light used?
- (a)
5890\(\mathring { A } \)
- (b)
\(5000\mathring { A } \)
- (c)
\(6000\mathring { A } \)
- (d)
None of these
In an arrangement of double slit, the slits are illuminated by the light wavelength 600nm.Find the distance of the first point on the screen from the central maximum where intensity is 75% of the central maximum.The screen is 1 m away and slits are 2.1 mm apart
- (a)
\(4.8\times { 10 }^{ -6 }\)m
- (b)
\(4.8\times { 10 }^{ -3 }\)m
- (c)
\(4.8\times { 10 }^{ -5 }\)m
- (d)
None of the above
Soap bubble looks coloured due to
- (a)
dispersion
- (b)
reflection
- (c)
interference
- (d)
any one of these
In a biprism experiment, by using light of wavelength 5000\(\mathring { A } \), 5 mm wide fringes are obtained on a screen 1.0 m away from coherent sources.The separation between two coherent sources is
- (a)
1.0 mm
- (b)
0.1 mm
- (c)
0.05 mm
- (d)
0.01 mm
In young's double slit experiment, two slits act as coherent sources of equal amplitude A and of wavelength \(\lambda\).In another experiment with the same set up, the two slits are sources of again of same amplitude A and wavelength \(\lambda\) but are incoherent.The ratio of intensity at the mid-point of the screen in the first case to that in the second case i.e,(\({ I }_ { 1 }/{ I } { 2 }\)) is
- (a)
1:2
- (b)
2:1
- (c)
1:4
- (d)
4:1
To observe diffraction, the size of an aperture
- (a)
should be of the same order as wavelength of light used
- (b)
should be much larger than the wavelength
- (c)
have no relation to wavelength
- (d)
should be exactly \(\lambda/2\)
The phenomenon of diffraction can be treated as the phenomenon of interference of light if the number of coherent sources is
- (a)
one
- (b)
two
- (c)
zero
- (d)
infinity
A diffraction pattern is obtained using a beam of red light.What will happen if red light is replaced by blue light?
- (a)
No change
- (b)
diffraction brands become narrower and crowded together
- (c)
bands become broader and farther apart
- (d)
bands disappear
A single slit of width d is placed in the path of beam of wavelength \(\lambda\). The angular width of the principal maximum obtained is
- (a)
\(\frac { \lambda }{ d } \)
- (b)
\(\pm \frac { \lambda }{ d } \)
- (c)
\(\frac {2 \lambda }{ d } \)
- (d)
\(\frac { 2d }{ \lambda } \)
The fraunhofer diffraction pattern of a single slit is formed in the focal plane of a convex lens of focal length f.The width of slit is 'a' and the distance between the slit and screen is d. The convex lens is placed.
- (a)
close to the slit
- (b)
close to the screen
- (c)
at a distance d/2 from the slit
- (d)
anywhere in between slit and screen
The Fraunhofer diffraction pattern of a single slit is formed in the focal plane of a converging lens of focal length 1 m. the width of slit is 0.3 mm.If third minimum is formed at a distance of 5 mm from central maximum, then wavelength of light will be
- (a)
5000\(\mathring { A } \)
- (b)
\(2500\mathring { A } \)
- (c)
\(7500\mathring { A } \)
- (d)
\(8500\mathring { A } \)
The polariser is used to
- (a)
reduce intensity of light
- (b)
produce polarised light
- (c)
increase intensity of light
- (d)
produce unpolarised light
A rocket is going away from the earth at a speed 0.2 c, where c=speed of light.It emits signals of frequency \(4\times { 10 }^{ 7 }Hz\).What will be frequency observed by an observer on the earth?
- (a)
\(4\times { 10 }^{ 6 }Hz\)
- (b)
\(3.2\times { 10 }^{ 7 }Hz\)
- (c)
\(3\times { 10 }^{ 6 }Hz\)
- (d)
\(5\times { 10 }^{ 7 }Hz\)
The wavelength of light observed on the earth, from a moving star is found to decrease by 0.05%.Relative to the earth, the star is
- (a)
moving away with a velocity of \(1.5\times { 10 }^{ 5 }{ ms }^{ -1 }\)
- (b)
moving closer with a velocity of \(1.5\times { 10 }^{ 5 }{ ms }^{ -1 }\)
- (c)
moving away with a velocity of \(1.5\times { 10 }^{ 4 }{ ms }^{ -1 }\)
- (d)
moving closer with a velocity of \(1.5\times { 10 }^{ 4 }{ ms }^{ -1 }\)
For coherent sources
- (a)
amplitude must be same
- (b)
a constant phase difference is required
- (c)
Both (a) and (b) are correct
- (d)
Both (a) and (b) are incorrect
Two waves of same frequency and same amplitude from two monochromatic sources are allowed to superpose at a certain point. If in one case, the phase difference is 0° and in other case, it is \(\pi /2\), then the ratio of the intensities in the two cases will be
- (a)
1 : 1
- (b)
2 : 1
- (c)
4 : 1
- (d)
None of the above
The maximum intensity of fringes in Young's experiment is I. If one of the slit is closed, then the intensity at that place becomes I0. Which of the following relation is true?
- (a)
I = I 0
- (b)
I = 2I0
- (c)
I = 4I0
- (d)
I = 0
A beam of ordinary unpolarised light passes through a tourmaline crystal C1 and then it passes through another tourmaline crystal C2 , which is oriented such that its principal plane is parallel to that of C2. The intensity of emergent light is I0. Now, C2 is rotated by 60° about the ray. The emergent ray will have intensity
- (a)
\(2{ I }_{ 0 }\)
- (b)
\({ I }_{ 0 }/\sqrt { 2 } \)
- (c)
\({ I }_{ 0 }/{ 4 } \)
- (d)
\({ I }_{ 0 }/\sqrt { 2 } \)
The ratio of the intensities of successive maxima is the diffraction pattern due to single slit is
- (a)
1 : 4 : 9
- (b)
1 : 2 : 3
- (c)
\(1:\frac { 4 }{ 9{ \pi }^{ 2 } } :\frac { 4 }{ 25{ \pi }^{ 2 } } \)
- (d)
\(1:\frac { 4 }{ { \pi }^{ 2 } } :\frac { 9 }{ { \pi }^{ 2 } } \)
In a Young's double slit experiment, the two slits acts as coherent sources of waves of equal amplitude A and wavelength \(\lambda \). In another experiment with the same arrangement, the two slits are made to act as incoherent sources of waves of same amplitude and wavelength. If the intensity at the middle point of the screen in the first case is I1 and in the second case is I2, then the ratio \(\frac { { I }_{ 1 } }{ { I }_{ 2 } } \) is
- (a)
4
- (b)
2
- (c)
1
- (d)
0.5