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Question Bank No: 3

1. The Young's modulus for steel is $2 \times 10^{11} {Nm}^{- 2} .$ If the inter atomic spacing for the metals is $2.8 A^{0}$ , the increase in the inter atomic spacing for a force of $10^{9} {Nm}^{- 2}$ is

a)		$1.4 \times 10^{- 3} A^{0}$
b)		$1.4 \times 10^{- 2} A^{0}$
c)		$1.4 \times 10^{- 1} A^{0}$
d)		$1.4 A^{0}$

2. If young's double slit experiment is performed in water,

a)		the fringe width will decreases
b)		the fringe width will increase
c)		the fringe width will remain unchanged
d)		there will be no fringe

3. In an interference pattern the position of zeroth order maxima is 4.8mm from a certain point P on the screen. The fringe width is 0.2mm. The position of second maxima from point P is

a)		5.1 mm
b)		5 mm
c)		40 mm
d)		5.2 mm

4. In young's double slit experiment when violet light of wave length 4358 $Å$ is used, then 84 fringes are seen in the field of view, but when sodium light of certain wave length is used, then 62 fringes are seen in the field of view, the wave length of sodium light is

a)		6893 $Å$
b)		5904 $Å$
c)		5523 $Å$
d)		6429 $Å$

5. When two coherent monochromatic light beams of intensities I and 4I are superimposed, what are the maximum and minimum possible intensities in the resulting beams?

a)		5I and I
b)		5I and 3I
c)		9I and I
d)		9I and 3I

6. In young's double slit experiment with monochromatic light of wave length 600nm, the distance between slits is $10^{- 3} m$ . For changing fringe width by $3 \times 10^{- 5} m$

a)		the screen is moved away from the slits by 5cm
b)		the screen is moved by 5cm towards the slits
c)		the screen is moved by 3cm towards the slits
d)		both (a) and (b) are correct

7. In a young's experiment, one of the slit is covered with a transparent sheet of thickness $3.6 \times 10^{- 3}$ cm due to which position of central fringe shifts to a position originally occupied by 30th bright fringe. The refractive index of the sheet, if $λ = 6000 Å$ is

a)		1.5
b)		1.2
c)		1.3
d)		1.7

8. The resulting intensity after interference of two coherent waves represented by $y_{1} = a_{1} \cos ω t$ and $y_{2} = a_{2} \cos (\frac{π}{2} - ω t)$ will be

a)		$a_{1} - a_{2}$
b)		$a_{1} + a_{2}$
c)		$a_{1}^{2} - a_{2}^{2}$
d)		$a_{1}^{2} + a_{2}^{2}$

9. Newton's rings are observed by keeping a spherical surface of 100cm radius on a plane glass plate. The wave length of light used is 5880 $Å .$ If the diameter of the 15th bright ring is 0.59cm, the diameter of the 5th ring is

a)		0.226cm
b)		0.446cm
c)		0.336cm
d)		0.556cm

10. The slit width, when a light of wavelength 6500 $Å$ is incident on a slit, if first minima for red light is at $30^{0}$

a)		$1 \times 10^{- 6} m$
b)		$5.2 \times 10^{- 6} m$
c)		$1.3 \times 10^{- 6} m$
d)		$2.6 \times 10^{- 6} m$