YDSE Problems I

Q. In YDSE d=2mm D=2m wavelength=500nm.Intensity of 2 slits are I and 9I then find intensity at y=1/6mm.

Q.

In a Young’s double-slit experiment, the path difference, at a certain point on the screen between two interfering waves is ${(1/8)}^{th}$ of wavelength. The ratio of the intensity at this point to that at the centre of a bright fringe is close to

1. $0.74$

2. $0.80$

3. $0.85$

4. $0.94$

Q. The relative permittivity of distilled water is $81$. The velocity of light in it will be :
(Given ${\mu }_r=1$)

1. $4.33\times {10}^7\text{m/s}$
2. $3.33\times {10}^7\text{m/s}$
3. $5.33\times {10}^7\text{m/s}$
4. $2.33\times {10}^7\text{m/s}$

Q. In an interference experiment, the ratio of amplitudes of coherent waves is $\frac{a_1}{a_2}=\frac{1}{3}$. The ratio of maximum and minimum intensities of fringes will be

1. $4$
2. $2$
3. $9$
4. $18$

Q. In double-slit experiment using light of wavelength 600 nm, the angular width of a fringe formed on a distant screen is 0.1°. What is the spacing between the two slits?

Q. White light is incident normally on a glass plate $\left(\text{in air}\right)$ of thickness $500\text{nm}$ and refractive index of $1.5$. The wavelength $\left(\text{in nm}\right)$ in the visible region $\left(\text{400 nm-700 nm}\right)$ that is strongly reflected by the plate is

1. $450$
2. $600$
3. $400$
4. $500$

Q. In the Young's double slit experiment, the distance between the slits varies in time as $d\left(t\right)=d_0+a_0\sin \omega t$; where $d_0,\omega$ and $a_0$ are constants. The difference between the largest fringe width and the smallest fringe width, obtained over time, is given as :

1. $\frac{2\lambda D\left(d_0\right)}{(d_0^2-a_0^2)}$
2. $\frac{\lambda D}{d_0^2}{a}_0$
3. $\frac{\lambda D}{d_0+a_0}$
4. $\frac{2\lambda D{a}_0}{(d_0^2-a_0^2)}$

Q.

In an interference arrangement similar to Youngs double slit experiment, the slits S₁ and S₂ are illuminated with coherent microwave sources each of frequency 10⁶ Hz. The sources are synchronized to have zero phase difference. The slits are separated by distance d = 150 m. The intensity I(θ)is measured as a function of q, where q is defined as shown. If I₀ is maximum intensity, then I(θ) for 0≤θ≤90° is given by

1. 

2. 

3. 

4. 

Q.

An optical fibre $(\mu =1.72)$ is surrounded by a glass coating $(\mu =1.50)$. Find the critical angle for total internal reflection at the fibre-glass interface.

Q. A parallel beam of diameter $d$ is incident on the air-glass interface, as shown in figure. The diameter of the refracted light beam is

$(d=3\text{mm},\theta ={45}^{\circ }\text{and}\frac{n_{glass}}{n_{air}}=\frac{3}{2})$

1. $\sqrt{12}\text{mm}$
2. $\sqrt{14}\text{mm}$
3. $\sqrt{6}\text{mm}$
4. $4.5\text{mm}$

Q. 3. Width of the fringes is equal ininterference. In diffraction they are neverequal. IN DIFFRACTION WIDTH OF MAXIMA AND MINIMA IS SAME SO WHY IT SAYS THEY ARE NEVER EQUAL?

Q. Two coherent source whose intensity ratio is 81:1 produce interference frimges. Calculate the ratio of intensity of maxima and minima in the fringe system

Q.

In Youngs double slit experiment, a third slit is made in between the double slits. Then,

1. Fringes of unequal width are formed.

2. Contrast between bright and dark fringes is reduced.

3. Intensity of fringes totally disappears.

4. Only bright light is observed on the screen.

Q. A simply supported beam has an effective span of 20 m. The limiting ratio of span to effective depth as per IS 456: 2000 is .

Q.

In youngs double slit experiment, the ratio of intensities of bright and dark bands is $16$ which means:

1. The ratio of their amplitude is$5$.

2. Intensities of individual sources are $25$ and$9$ units respectively.

3. The ratio of their amplitudes is $4$.

4. Intensities of individual sources are $4$ and $3$ units respectively.

Q.

In a young's double slit experiment, two narrow vertical slits placed 0.800 mm apart are illuminated by the same source of yelow light of wavelength 589 nm. How far are the adjacent bright bands in the interference pattern observed on a screen 2.00 m away?

Q. Two trees are at distance of 3.14 m from each other. What should be the maximum distance of an observer from tree to see them separately. 1. 21.6 km 2. 10.8 km 3. 15 km 4. 25.2 km

Q. In young's double slit experiment the fringe width with light of wave length 6000 A is found to be 4.0mm. What will be the fringe width if light of wavelength 4800 A is used?

1. 4.8mm
2. 2.8mm
   
3. 3.2mm
   
4. 4.0mm
   

Q. In the Young's double slit experiment shown in the figure, the medium between slit plane and the screen has refractive index varying with time as $n=n_0+kt$, then

1. The y co-ordinates of central maximum is $\frac{D\sin \varphi }{n_0+kt}$.
2. Velocity of central maximum as a function of time is $\frac{-kD\cos \varphi }{(n_0+kt{)}^2}$.
3. If a glass plate of small thickness $p$ is placed in front of $S_1$, then to form central maximum at O, refractive index of glass should vary as $n_0+kt+\frac{d\sin \varphi }{p}$.
4. If a glass plate of small thickness $p$ is placed in front of $S_1$, then to form central maxima at O, refractive index of glass should vary as $n_0+kt+\frac{d\cos \varphi }{p}$

Q.

In a Young’s double slit experiment the slit separation is 0.5 m from the slits. For a monochromatic light of wavelength 500 nm, the distance of $3^{rd}$ maxima from $2^{nd}$ minima on the other side is

1. 22.5 mm

2. 2.75 mm

3. 2.25 mm

4. Question is incorrect

Q. How to obtain maixma and minima in single slit diffraction and path difference?

Q. The ratio of maximum intensity and minimum intensity obtained in the interference of waves emitted by two coherent sources is 121 : 81. The ratio of amplitude of two coherent sources will be

1. 1 : 10
2. 10 : 1
3. 81 : 121
4. 121 : 81

Q. Q.13 When a metallic surface is illuminated with radiation of wavelength lamda , the stopping potential is V .if same surface is illuminated with radiation of wavelength 2 lamda , the stopping potential is V/4. the threshold wavelength for the metallic surface is

Q. ntIn a single slit diffraction of light of wavelengths by a slit of width e, the size of the central maximum on a screen at a distance b is?n

Q. In a Young's double slit experiment, $d=1\text{mm},\lambda =6000\mathring{\text{A}}$ and $D=1\text{m}$. The two slits have equal intensity. The minimum distance between two points on the screen, having $75\%$ intensity of the maximum intensity is,

1. $0.45\text{mm}$
2. $0.40\text{mm}$
3. $0.30\text{mm}$
4. $0.20\text{mm}$

Q.

In a Youngs double slit experiment, constructive interference is produced at a certain point P. The intensities of light at P due to the individual sources are $4$ and $9$ units. The resultant intensity at point P will be

1. $13units$

2. $25units$

3. $\sqrt{97}units$

4. $5units$

Q. A single slit is illuminated with a parallel beam of light of wavelength 6000 $A^{\circ }$ and a diffraction pattern is obtained on a screen 1.2 m away from the slit. Distance between position of zero intensity on both side of central maxima is found to be 3.5 mm, then width of slit is

1. 0.4 mm
2. 1.2 mm
3. 0.7 mm
4. 0.8 mm

Q. A ray of light falls on a transparent sphere with its centre at $\text{C}$, as shown in the figure. The ray emerges from the sphere parallel to the line AB. Then, the refractive index of the sphere is

1. $\sqrt{2}$
2. $\sqrt{3}$
3. $\frac{3}{2}$
4. $\frac{1}{2}$

Q.

Two narrowsslits emitting light in phase are separated by adistance of 1.0 cm. The wavelength of the light is $5.0\times {10}^{-7}$ m. The interference pattern in observed on a screen placed at a distance of 1.0 m. (a) Find the separation between the consecutive maxima. can you expect to distingish between these maxima? (b) Find the separation between the sources which will give a separation of 1.0 mm between the cnsecutive maxima.

Q.

Two coherent point sources $S_1$ and $S_2$ vibrating in phase emit light of wavelength $\lambda$0 the separation between the sources is $2\lambda .$ consider a line passing thrrough $S_2$ and perpendicular to the line$S_1{S}_2$ What is the smallest distance from $S_2$ where is the smallest distance from $S_2$ where a minimum of intensity occurs?