Fringe Width in YDSE

Q.

Why Sodium light used in polarimeters?

Q.

In a Youngs double slit experiment with slit separation $0.1mm$, one observes a bright fringe at angle $1/40rad$ by using light of wavelength ${\lambda }_1$. When the light of wavelength ${\lambda }_2$ is used a bright fringe is seen at the same angle in the same setup. Given that ${\lambda }_1$ and ${\lambda }_2$ are in visible range $(380nmto740nm)$, their values are:

1. $380nm,525nm$

2. $625nm,500nm$

3. $380nm,500nm$

4. $400nm,500nm$

Q. If Young's double slit experiment is performed in water,
(a) the fringe width will decrease
(b) the fringe width will increase
(c) the fringe width will remain unchanged
(d) there will be no fringe

Q. In Young’s double slit experiment, the distance between the slits is 0.2 mm and the distance of the screen from the slits is 2 m. If light of wavelength 500 nm is used, find the number of fringes formed between two points separated by 1 cm on the screen.

1. 1
2. 2
3. 3
4. 4

Q.

In YDSE monochromatic light of wavelength$600nm$ incident of slits as shown in figure.

If $S_1{S}_2=3mm$, $OP=11mm$ then

1. If $\alpha =\frac{0.36}{\pi }$ degree then destructive interfaces at point $P$.
2. If $\alpha =\frac{0.36}{\pi }$ degree then constructive interfaces at point $O$.
3. If $\alpha =0$ then constructive interfaces at $O$
4. Fringe width depends on $\alpha$.

Q.

In Young's double slit experiment the slits are 0.5 mm apart and interference is observed on a screen placed at a distance of 100 cm from the slits. It is found that the 9th bright fringe and 3rd dark fringe from the centre are 9mm apart. What is the wavelength of light used?

1. 2000A

2. 4000A

3. 6000A

4. 8000A

Q. A source emitting light of wavelengths 480 nm and 600 nm is used in a double-slit interference experiment. The separation between the slits is 0⋅25 mm and the interference is observed on a screen placed at 150 cm from the slits. Find the linear separation between the first maximum (next to the central maximum) corresponding to the two wavelengths.

Q. Coherent electron beam is being used in YDSE. On increasing accelerating voltage, fringe width will

1. decrease
2. remain unchanged
3. increase
4. may increase or decrease

Q. In YDSE, 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.

1. 12
2. 18
3. 24
4. 30

Q. In a Lloyd's single mirror experiment, the distance between the slit source and its image is $5mm$. The screen is at a distance of $1\text{m}$ from the source. The fringe width is observed to be $0.1mm$. Then the wavelength of light used is

1. $5460\stackrel{\circ }{A}$
2. $5000\stackrel{\circ }{A}$
3. $6460\stackrel{\circ }{A}$
4. $4000\stackrel{\circ }{A}$

Q. A parallel beam of white light is incident normally on a water film 1.0 × 10⁻⁴ cm thick. Find the wavelengths in the visible range (400 nm − 700 nm) which are strongly transmitted by the film. Refractive index of water = 1.33.

Q. As the wavelength is increased from violet to red, the luminosity
(a) continuously increases
(b) continuously decreases
(c) increases then decreases
(d) decreases then increases

Q. The Young’s experiment is first performed with sodium light and then with Neon light of the same intensity.
Which of the following effects will be noticed?

1. The fringes will disappear
2. The fringes will become less distinct
3. The fringe width will increase
4. The fringe width will decrease

Q. A monochromatic beam of electrons accelerated by a potential difference $V$ falls normally on the plane containing two narrow slits separated by a distance $d$. The interference pattern is observed on a screen parallel to the plane of the slits and at a distance of $D$ from the slits. Fringe width is found to be $w_1$. When electron beam is accelerated by the potential difference $4V,$ the fringe width becomes $w_2$. Find the ratio $\frac{w_1}{w_2}$. (Given d << D)

Q. Laser light of wavelength $630nm$ incident on a pair of slits produces an interference pattern in which the bright fringes are separated by $8.1mm$. A second light produces an interference pattern in which the fringes are separated by $7.2mm$. Then the wavelength of the second light will be

1. $500nm$
2. $560nm$
3. $600nm$
4. $660nm$

Q. A soap film of thickness 0.0011 mm appears dark when seen by the reflected light of wavelength 580 nm. What is the index of refraction of the soap solution if it is known to be between 1.2 and 1.5?

Q. In young's double slit experiment, the slit separation is 1.0 mm and the screen is placed at a distance of 1.0m from the plane of the slits. If the slit separation is changed by 0.05 mm, the fringe width changes by 0.03mm. The wavelength of light used is

1. 4000A
2. 5000A
3. 6000A
4. 7000A

Q. In Young's double slit interference experiment, the wavelength of light used is $6000\dot{A}$. If the path difference between waves reaching a point P on the screen is 1.5 microns, then at that point P

1. Second maxima occurs
2. Second minima occurs
3. Third minima occurs
4. Third maxima occurs

Q.

Fringe width observed in the Young's double-slit experiment is $\beta$ . If the frequency of the source is doubled, the fringe width will

1. $Remain\beta$
2. $becomes\frac{\beta }{2}$
3. $becomes2\beta$
4. $becomes\frac{3\beta }{2}$

Q. Two slits spaced 0.25 mm apart are placed at 0.75 m from a screen and illuminated by coherent light with a wavelength of 650 nm. The intensity at the centre of the central maximum $(\theta =0^{\circ })$ is $I_0$. The distance on the screen from the centre of central maximum to the point where the intensity has fallen to $\frac{I_0}{2}$ is nearly

1. 0.1 mm
2. 25 mm
3. 0.4 mm
4. 0.5 mm

Q.

In a certain double slit experimental arrangement interference fringes of width 1.0 mm each are observed when light of wavelength 5000 Å is used. Keeping the set up unaltered, if the source is replaced by another source of wavelength 6000 Å, the fringe width will be

[CPMT 1988]

1. 0.5 mm

2. 1.0 mm

3. 1.2 mm

4. 1.5 mm

Q. Two slits separated by 0.200 mm are to be used in Young’s double – slit experiment. Immediately behind the slits in a lens of focal length 0.500 m used to form the interference pattern on a screen located in the focal plane of the lens. What is wavelength of a monochromatic light source used to illuminate the slits if adjacent maxima of the interference pattern are separated by 1.00 mm?

1. 400 nm
2. 500 nm
3. 600 nm
4. 700 nm

Q. A parallel beam of light of wavelength $6000\dot{A}$ is incident normally on a slit of width $0.2\text{mm}$. The diffraction pattern is observed on a screen which is placed at the focal plane of a convex lens of focal length $50\text{cm}$. If the lens is placed close to the slit. The distance between the minimum on both sides of the central maximum will be

1. $1\text{mm}$
2. $3\text{mm}$
3. $2\text{mm}$
4. $4\text{mm}$

Q. In a double – slit experiment, instead of taking slits of equal width, one slit is made twice as wide as the other. Then in the interference pattern

1. The intensities of both the maxima and the minima increase.
2. The intensity of the maxima increases and the minimum has zero intensity.
3. The intensity of the maxima decreases and that of the minima increases.
4. The intensity of the maxima decreases and the minima has zero intensity.

Q. In the figure $S_1$ and $S_2$ are two narrow slits illuminated by light of wavelength ${}^{\prime }{\lambda }^{\prime }$ and they ae in phase. `P' is a point on the screen which corresponds to 4th minimum then the path difference $S_{2}P–S_{1}P$ is equal to

1. $4\lambda$
2. $5\frac{\lambda }{2}$
   
3. $7\frac{\lambda }{2}$
   
4. $2\lambda$

Q. A parallel beam of light of wavelength $6000\mathring{A}$ gets diffracted by a single slit of width $0.3\text{mm}$. The angular position of the first minima of diffracted light is,

1. $8\times {10}^{-3}\text{rad}$
2. $2\times {10}^{-3}\text{rad}$
3. $3\times {10}^{-3}\text{rad}$
4. $6\times {10}^{-3}\text{rad}$