Video Lecture
Theory For Making Notes
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Practice Questions (Basic Level)
1.
Two coherent sources of light can be obtained by
(a) Two different lamps
(b) Two different lamps but of the same power
(c) Two different lamps of same power and having the same colour
(d) None of the above
Ans (d)
2.
Two coherent monochromatic light beams of intensities I and 4I are superposed. The maximum and minimum possible intensities in the resulting beam are
(a) 5I and I
(b) 5I and 3I
(c) 9I and I
(d) 9I and 3I
Ans (c)
3.
If the ratio of intensities of two waves is 1 : 25, then the ratio of their amplitudes will be
(a) 1 : 25
(b) 5 : 1
(c) 26 : 24
(d) 1 : 5
Ans (d)
4.
Two identical light sources S1 and S2 emit light of same wavelength λ. These light rays will exhibit interference if
(a) Their phase differences remain constant
(b) Their phases are distributed randomly
(c) Their light intensities remain constant
(d) Their light intensities change randomly
Ans (a)
5.
If two waves represented by {{y}_{1}}=4\sin \omega t and {{y}_{2}}=3\sin \left( {\omega t+\frac{\pi }{3}} \right) interfere at a point, the amplitude of the resulting wave will be about
(a) 7
(b) 6
(c) 5
(d) 3.5
Ans (b)
6.
If the ratio of amplitude of two waves is 4 : 3, then the ratio of maximum and minimum intensity is
(a) 16 : 18
(b) 18 : 16
(c) 49 : 1
(d) 94 : 1
Ans (c)
7.
Coherent sources are those sources for which
(a) Phase difference remain constant
(b) Frequency remains constant
(c) Both phase difference and frequency remains constant
(d) None of these
Ans (c)
8.
Two waves are represented by the equations {{y}_{1}}=a\sin \omega t and {{y}_{2}}=a\cos \omega t. The first wave
(a) Leads the second by π
(b) Lags the second by π
(c) Leads the second by \frac{\pi }{2}
(d) Lags the second by \frac{\pi }{2}
Ans (d)
9.
Four coherent waves are represented by
(i) y = a1 sinw t
(ii) y={{a}_{2}}\sin (\omega \,t+\varphi )
(iii) y={{a}_{1}}\sin 2\omega \,t
(iv) y={{a}_{2}}\sin 2(\,\omega \,t+\varphi )
Interference may be observed due to superposition of
(a) (i) and (ii) & (i) and (iii)
(b) (i) and (iii) only
(c) (ii) and (iv) only
(d) (i) and (ii) & (iii) and (iv)
Ans : (d)
10.
Young’s experiment establishes that
(a) Light consists of waves
(b) Light consists of particles
(c) Light consists of neither particles nor waves
(d) Light consists of both particles and waves
Ans (a)
11.
In the interference pattern, energy is
(a) Created at the position of maxima
(b) Destroyed at the position of minima
(c) Conserved but is redistributed
(d) None of the above
Ans (c)
12.
Monochromatic green light of wavelength 5\times {{10}^{{-7}}}milluminates a pair of slits 1 mm The separation of bright lines on the interference pattern formed on a screen 2 m away is
(a) 0.25 mm
(b) 0.1 mm
(c) 1.0 mm
(d) 0.01 mm
Ans (c)
13.
The figure shows a double slit experiment P and Q are the slits. The path lengths PX and QX are n\lambda and (n+2)\lambda respectively, where n is a whole number and l is the wavelength. Taking the central fringe as zero, what is formed at X
(a) First bright
(b) First dark
(c) Second bright
(d) Second dark
Ans (c)
14.
In Young’s double slit experiment, a glass plate is placed before a slit which absorbs half the intensity of light. Under this case
(a) The brightness of fringes decreases
(b) The fringe width decreases
(c) No fringes will be observed
(d) The bright fringes become fainter and the dark fringes have finite light intensity
Ans (d)
15.
In Young’s experiment, the distance between the slits is reduced to half and the distance between the slit and screen is doubled, then the fringe width
(a) Will not change
(b) Will become half
(c) Will be doubled
(d) Will become four times
Ans (d)
16.
The Young’s experiment is performed with the lights of blue (l = 4360 Å) and green colour (l = 5460 Å), If the distance of the 4th fringe from the centre is x, then
(a) x (Blue) = x (Green)
(b) x (Blue)> x (Green)
(c) x (Blue) < x (Green)
(d) \frac{{x(Blue)}}{{x(Green)}}=\frac{{5460}}{{4360}}
Ans (c)
17.
In Young’s experiment, light of wavelength 4000 Å is used to produce bright fringes of width 0.6 mm, at a distance of 2 meters. If the whole apparatus is dipped in a liquid of refractive index 1.5, then fringe width will be
(a) 0.2 mm
(b) 0.3 mm
(c) 0.4 mm
(d) 1.2 mm
Ans (c)
18.
In a Young’s double slit experiment, the fringe width will remain same, if (D = distance between screen and plane of slits, d = separation between two slits and l = wavelength of light used) (a) Both l and D are doubled
(b) Both d and D are doubled
(c) D is doubled but d is halved
(d) l is doubled but d is halved
Ans (b)
19.
In Young’s double slit experiment, angular width of fringes is 0.20o for sodium light of wavelength 5890 Å. If complete system is dipped in water, then angular width of fringes becomes
(a) 0.11o
(b) 0.15o
(c) 0.22o
(d) 0.30
Ans (b)
20.
In Young’s double slit experiment, the distance between the slits is 1 mm and that between slit and screen is 1 meter and 10th fringe is 5 mm away from the central bright fringe, then wavelength of light used will be
(a) 5000 Å
(b) 6000 Å
(c) 7000 Å
(d) 8000 Å
Ans (a)
21.
In Young’s double slit experiment, a mica slit of thickness t and refractive index m is introduced in the ray from the first source S1. By how much distance the fringes pattern will be displaced
(a) \frac{d}{D}(\mu -1)\ t
(b) \frac{D}{d}(\mu -1)\ t
(c) \frac{d}{{(\mu -1)D}}
(d) \frac{D}{d}(\mu -1)
Ans (b)
22.
If a white light is used in Young’s double slit experiments then a very large number of coloured fringes can be seen
(a) With first order violet fringes being closer to the central white fringes
(b) First order red fringes being closer to the central white fringes
(c) With a central white fringe
(d) With a central black fringe
Ans (c)
23.
In a Young’s double slit experiment, 12 fringes are observed to be formed in a certain segment of the screen when light of wavelength 600 nm is used. If the wavelength of light is changed to 400 nm, number of fringes observed in the same segment of the screen is given by
(a) 12
(b) 18
(c) 24
(d) 30
Ans (b)
24.
In Young’s double slit experiment, distance between two sources is 0.1 mm. The distance of screen from the sources is 20 cm. Wavelength of light used is 5460 Å. Then angular position of the first dark fringe is
(a) 0.08°
(b) 0.16°
(c) 0.20°
(d) 0.313°
Ans (d)
Practice Questions (JEE Main Level)
1.
Two speakers are 1 m apart and emit sound of frequency 1000 Hz in phase. A listener walks along a line that is parallel to the line joining the speakers and 8 m away from their midpoint. What is the separation between the central maximum and the first minimum in loudness? Take the speed of sound to be 340 m/s.
(a)2.00 m
(b) 1.50 m
(c) 1.36 m
(d) 1.00 m
Ans (c)
Practice Questions (JEE Advance Level)
1.
For the arrangement of two speakers shown in figure, assume S1 is p rad out of phase with S2. The frequency is 500 Hz. What is the minimum value of d for which the intensity at P is a maximum? Take the speed of sound to be 340 m/s.
(a) 1.00 m
(b) 1.25 m
(c) 1.50 m
(d) 1.68 m
Ans (d)