Video Lecture
Theory For Making Notes
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Practice Questions (Basic Level)
1.
Soap bubble appears coloured due to the phenomenon of
(a) Interference
(b) Diffraction
(c) Dispersion
(d) Reflection
Ans (a)
2.
On a rainy day, a small oil film on water show brilliant colours. This is due to
(a) Dispersion of light
(b) Interference of light
(c) Absorption of light
(d) Scattering of light
Ans (b)
3.
The phase difference between incident wave and reflected wave is 180° when light ray
(a) Enters into glass from air
(b) Enters into air from glass
(c) Enters into glass from diamond
(d) Enters into water from glass
Ans (a)
4.
What causes changes in the colours of the soap or oil films for the given beam of light
(a) Angle of incidence
(b) Angle of reflection
(c) Thickness of film
(d) None of these
Ans (c)
5.
In Fresnel’s biprism (\mu =1.5) experiment the distance between source and biprism is 0.3 m and that between biprism and screen is 0.7m and angle of prism is 1°. The fringe width with light of wavelength 6000 Å will be
(a) 3 cm
(b) 0.011 cm
(c) 2 cm
(d) 4 cm
Ans (b)
6.
In Fresnel’s biprism experiment, on increasing the prism angle, fringe width will
(a) Increase
(b) Decrease
(c) Remain unchanged
(d) Depend on the position of object
Ans (b)
7.
If prism angle \alpha =1{}^\circ ,\ \mu =1.54,distance between screen and prism (b)=0.7\,m, distance between prism and source a=0.3\,m,\ \lambda =180\pi \ nm then in Fresnal biprism find the value of \beta (fringe width)
(a) {{10}^{{-4}}}m
(b) {{10}^{{-3}}}mm
(c) {{10}^{{-4}}}\times \pi m
(d) \pi \times {{10}^{{-3}}}m
Ans (a)
8.
If Fresnel’s biprism experiment as held in water inspite of air, then what will be the effect on fringe width
(a) Decrease
(b) Increase
(c) No effect
(d) None of these
Ans (a)
9.
What is the effect on Fresnel’s biprism experiment when the use of white light is made
(a) Fringe are affected
(b) Diffraction pattern is spread more
(c) Central fringe is white and all are coloured
(d) None of these
Ans (c)
10.
In which of the following is the interference due to the division of wave front
(a) Young’s double slit experiment
(b) Fresnel’s biprism experiment
(c) Lloyd’s mirror experiment
(d) Demonstration colours of thin film
Ans (b)
Practice Questions (JEE Main Level)
1.
A glass plate of refractive index 1.5 is coated with a thin layer of thickness t and refractive Index 1.8. Light of wavelength \displaystyle \lambda travelling in air is incident normally on the layer . It is partly reflected at the upper and the lower surfaces of the layer and the two reflected rays interfere. If \displaystyle \lambda = 648 nm, obtain the least value of t for which the rays interfere constructive
(a) 45 nm
(b) 90 nm
(c) 180 nm
(d) 135 nm
7.
In an air wedge experiment, monochromatic light of wavelength 500 nm is incident normally on the upper plate. When viewed from above, the distance of the centre of the fifth bright fringe from O is
(a) 1.125 mm
(b) 1 mm
(c) 1.63 mm
(d) none of these
Practice Questions (JEE Advance Level)
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