Physics - Wave Optics
Exam Duration: 45 Mins Total Questions : 30
Which of the following phenomena is not common to sound and light waves?
- (a)
Interference
- (b)
Diffraction
- (c)
Coherence
- (d)
Polarisation
In a double slit interference experiment,the distance between the slits is 0.05 cm and screen is 2m away from the slits. the wavelength of lights is \(8.0\times { 10 }^{ -5 }\)cm.The distance between successive fringes is
- (a)
0.24 cm
- (b)
0.16 cm
- (c)
0.32 cm
- (d)
0.48 cm
In young's double slit experiment,the fringe width is found to be 0.4mm.If the whole apparatus is immersed in water of refractive index 4/3, without disturbing the geometrical arrangement, the new fringe width will be
- (a)
0.30mm
- (b)
0.40mm
- (c)
0.53mm
- (d)
450 microns
In a certain double slit experimental arrangement,interference fringes of width 1.0mm each are observed when light of wavelength 5000\(\mathring { A } \) is observed.If the light source is replaced by wavelength 6000\(\mathring { A } \), the fringe width will be
- (a)
0.5mm
- (b)
1.0mm
- (c)
1.2mm
- (d)
1.5mm
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
For the sustained interference of light,the necessary conditiion is that the two sources should
- (a)
have constant phase difference
- (b)
have the same state of polarisation
- (c)
be close to each other
- (d)
have large distance apart from the screen
Two waves \({ y }_{ 1 }={ A }_{ 1 }\sin { (\omega t-{ \beta }_{ 1 }) } \)and\({ y }_{ 2 }={ A }_{ 2 }\sin { (\omega t-{ \beta }_{ 2 }) } \)superimpose to form a resultant wave whose amplitude is
- (a)
\(\sqrt { { A }_{ 1 }^{ 2 }+{ A }_{ 2 }^{ 2 }+2{ A }_{ 1 }{ A }_{ 2 }\cos { ({ \beta }_{ 1 }-{ \beta }_{ 2 }) } } \)
- (b)
\(\sqrt { { A }_{ 1 }^{ 2 }+{ A }_{ 2 }^{ 2 }+2{ A }_{ 1 }{ A }_{ 2 }\sin { ({ \beta }_{ 1 }-{ \beta }_{ 2 }) } } \)
- (c)
\({ A }_{ 1 }+{ A }_{ 2 }\)
- (d)
\(\left| { A }_{ 1 }+{ A }_{ 2 } \right| \)
In a wave, the path difference corresponding to a phase difference of \(\phi \)is
- (a)
\(\frac { \pi }{ 2\lambda } \phi \)
- (b)
\(\frac { \pi }{ \lambda } \phi \)
- (c)
\(\frac { \lambda }{ 2\pi } \phi \)
- (d)
\(\frac { \lambda }{ \pi } \phi \)
Two slits, 4mm apart, are illuminated by light of wavelength 6000\(\mathring { A } \). what will be the fringe width on a screen placed 2m from the slits?
- (a)
0.12 mm
- (b)
0.3 mm
- (c)
3.0 mm
- (d)
4.0 mm
In young's double slit experiment, two coherent sources are placed 0.90 mm apart and fringes are observed one metre away.If it produces second dark fringe at a distance of 1 mm from central fringe, the wavelength of monochromatic light used would be
- (a)
\(60\times { 10 }^{ -4 }cm\)
- (b)
\(10\times { 10 }^{ -4 }cm\)
- (c)
\(10\times { 10 }^{ -5 }cm\)
- (d)
\(6\times { 10 }^{ -5 }cm\)
In two separate setups of the young's double slit experiment, fringes of equal width are observed when lights of wavelengths in the ratio 1:2 are used.If the ratio of the slit separation in two cases is 2:1 ,the ratio of distances between the plane of slits and the screen, in the two setups is
- (a)
4:1
- (b)
1:1
- (c)
1:4
- (d)
2:1
In young's double slit experiment, the width of both slits \({ S } _ {1 }\)and \({ S } _ {2 }\)is same and equal to 'a'. what change is observed in interference pattern of young's double slit experiment, if one of the two slits, say \({ S } _ {1 }\), has width increased to 2a, keeping the width of \({ S } _ {2 }\) same (equal to a)?
- (a)
intensity of maxima increase and that of minima decreases
- (b)
intensity of maxima decreases and that of minima increases
- (c)
intensity of maxima and minima increases
- (d)
No change in intensity of maxima and minima is observed
oil floating on water looks coloured due to interference of light.The approximate thickness of oil for such effect to be visible is
- (a)
100 \(\mathring { A } \)
- (b)
10,000 \(\mathring { A } \)
- (c)
1 mm
- (d)
1 cm
In young's double slit experiment carried out with wavelength \(\lambda =5000\mathring { A } \), the distance between the slits is 0.2 mm and the screen is at 200 cm from the slits.The central maximum is at x=0.The third maximum will be at X equal to
- (a)
1.67 cm
- (b)
1.5 cm
- (c)
0.5 cm
- (d)
5.0 cm
Soap bubble looks coloured due to
- (a)
dispersion
- (b)
reflection
- (c)
interference
- (d)
any one of these
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
In young's experiment withone source and two slits, one slit is covered with black opaque paper. The fringes will
- (a)
be narrower
- (b)
be broader
- (c)
not be observed at all and the screen will have uniform illumination
- (d)
be observed with central broad maximum surrounded by alternate minima and maxima of unequal widths
Light is incident normally on a diffraction grating through which the first order diffraction is seen at \({ 32 }^{ \circ }\). the second order diffraction will be seen at
- (a)
\({ 48 }^{ \circ }\)
- (b)
\({ 64 }^{ \circ }\)
- (c)
\({ 80 }^{ \circ }\)
- (d)
There is no second order diffraction in this case
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)
\(8500\mathring { A } \)
When the light is incident on polarising angle which of the following is completely polarised?
- (a)
reflected light
- (b)
refracted light
- (c)
both (a) and (b)
- (d)
neither (a) nor (b)
The given light of unknown state of polarisation is passed through a nicol prism.On rotating the nicol prism through \({ 360 }^{ \circ }\), rwo positions of maxima and two positions of extinctions of light are absorved.Then the state of polarisation of the given light must be
- (a)
linear
- (b)
elliptical
- (c)
circular
- (d)
random
If a star is moving towards the earth, them the spectral lines are shifted towards
- (a)
red
- (b)
infra-red
- (c)
blue
- (d)
green
A star emitting light of \(5000\mathring { A } \) is receding away from the earth with a velocity of \(300{ kms }^{ -1 }\).The apparent wavelength of light is
- (a)
\(5000\mathring { A } \)
- (b)
\(5005\mathring { A } \)
- (c)
\(5010\mathring { A } \)
- (d)
\(5\mathring { A } \)
Which of the following does not change when a wave travels from one medium to another medium?
- (a)
wavelength
- (b)
frequency
- (c)
velocity
- (d)
amplitude
Consider sunlight incident on a slit of width \({ 10 }^{ 4 }\dot { A } \). The image seen through the slit shall
- (a)
be a fine sharp slit white in colour at the centre
- (b)
a bright slit white at the centre diffusing to zero intensity at the edges
- (c)
a bright slit white at the centre diffusing to regions of different colours
- (d)
only be a diffused slit white in colour
At two points P and Q on screen in Young's double slit experiment, waves from slits S1 and S2 have a path difference of 0 and \(\lambda /4\) respectively.The ratio of intensities at P and Q will be
- (a)
3 : 2
- (b)
2 : 1
- (c)
\(\sqrt{2} : 1\)
- (d)
4 : 1