Angular Position of Fringes in Diffraction

Q. Light of wavelength $6000\stackrel{\circ }{A}$ is incident normally on a slit of width $24\times {10}^{-5}\text{cm}$. What is the angular position of second minimum from central maximum?

1. ${30}^{\circ }$
2. ${45}^{\circ }$
3. ${60}^{\circ }$
4. ${15}^{\circ }$

Q. Light of wavelength 6328 $\dot{A}$ is incident on a slit having a width of 0.2 mm. The width of the central maximum, measured from minimum to minimum of the diffraction pattern on a screen 9.0 metre away will be about:

1. 0.36 degrees
2. 0.72 degrees
3. 0.09 degrees
4. 0.18 degrees

Q. in YDSE two pin holes are seperated by a dis†an ce 2.5 lambda where lambda ia wavelength of light. initial phase difference is zero. a screen is placed perpendicular to line joining two pin holes. at the centre of screen . we obtain 1. a minima 2. a maxima 3. neither maxima nor minima 4. information not sufficient

Q. A parallel monochromatic beam of light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam. At the first minimum of the diffraction pattern, the phase difference between the rays coming from the two edges of the slit is

1. $0$
2. $\frac{\pi }{2}$
3. $\pi$
4. $2\pi$

Q. 11.An unpolarised beam of intensity Io is incident on a pair of nicols making an angle of 60 degree with each other.The intensity of light emerging from the pair is

Q.

A Young’s double-slit experiment is performed using monochromatic light of wavelength $\lambda$. The intensity of light at a point on the screen, where the path difference is $\lambda$, is $k$ units. The intensity of light at a point where the path difference is $\frac{\lambda }{6}$ is given by $\frac{nk}{12}$, where $n$ is an integer. The value of $n$ is __________.

Q. Two separate monochromatic light beams A and B of the same intensity are falling normally on a unit area of metallic surface their wavelength Lambda A and Lambda B respectively assuming that all the incident light is used in ejecting the photoelectrons the ratio of number of photoelectrons from the beiam A to that from beam B is.

Q. In a Young's double slit experiment, the slits are placed $0.320\text{mm}$ apart. Light of wavelength $\lambda =500\text{nm}$ is incident on the slits. The total number of bright fringes that are observed in the angular range $-{30}^{\circ }\le \theta \le {30}^{\circ }$ is

1. $641$
2. $321$
3. $320$
4. $640$

Q.

In Young’s double-slit experiment, the distance between two sources is $0.1mm$. The distance of the screen from the sources is $20cm$. The wavelength of light used is $5460\AA$ Then the angular position of the first dark fringe is$A$.

1. $0.{08}^o$

2. $0.{16}^o$

3. $0.{20}^o$

4. $0.{32}^o$

Q.

Light of wavelength $6000Angstrom$ falls on a single slit of width$0.1mm$. The second minimum will be formed for the angle of diffraction

1. $0.06rad$

2. $0.05rad$

3. $0.12rad$

4. $0.012rad$

Q. In a Young's double slit experiment, light of $500\text{nm}$ is used to produce an interference pattern. When the distance between the slits is $0.05\text{mm}$, the angular width (in degree) of the fringes formed on the distance screen is close to-

1. ${0.17}^{\circ }$
2. ${0.57}^{\circ }$
3. ${1.7}^{\circ }$
4. ${0.07}^{\circ }$

Q. Radius of $1^{st}$ dark ring of fraunhofers diffraction pattern produced by a circular aperture of radius 0.02 cm at focal plane of convex lens of focal length 20 cm and by light of wavelength $\lambda =600nm$ is

1. 0.7 mm
2. 0.36 mm
3. 1.3 mm
4. 2 cm

Q.

A parallel beam of light of wavelength 500 nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1 m away. It is observed that the first minimum is at a distance of 2.5 mm from the centre of the screen. Find the width of the slit.

Q.

Assuming the human pupil to have a radius of $0.25\mathrm{cm}$ and a comfortable viewing distance of $25\mathrm{cm}$, the minimum separation between two objects that the human eye can resolve at $500\mathrm{nm}$ wavelength is:

1. $30\mathrm{\mu m}$

2. $3\mathrm{\mu m}$

3. $300\mathrm{\mu m}$

4. $100\mathrm{\mu m}$

Q. (a) Describe briefly how a diffraction pattern is obtained on a screen due to a single narrow slit illuminated by a monochromatic source of light. Hence obtain the conditions for the angular width of secondary maxima and secondary minima.

(b) Two wavelengths of sodium light of 590 nm and 596 nm are used in turn to study the diffraction taking place at a single slit of aperture $2\times {10}^{-6}m$. The distance between the slit and the screen is 1.5 m. Calculate the separation between the positions of first maxima of the diffraction pattern obtained in the two cases.

Q. Light is incident on a glass plate $(\mu =1.5)$ such that angle of refraction is ${60}^{\circ }.$ Dark band is observed corresponding to the wave length of $6000\mathring{A}$. If the thickness of glass plate is $1.2\times {10}^{-3}\text{mm}.$ Calculate the order of the interference band for reflected system .

1. $4$
2. $5$
3. $3$
4. $2$

Q. In $YDSE$ shown in the Figure, a parallel beam of light is incident on the slits from a medium of refractive index $n_1$. The wavelength of light in the medium is ${\lambda }_1$. A transparent slab of thickness $t$ and refractive index $n_3$ is put in front of one slit. The refractive index of the medium between the beam and the plane of the slits is $n_2$. The phase difference between the light waves reaching point $O$ (symmetrical, relative to the slit) is

1. $\frac{2\pi }{n_1{\lambda }_1}(n_3-n_2)t$
2. $\frac{2\pi }{{\lambda }_1}(n_3-n_2)t$
3. $\frac{2\pi n_1}{n_2{\lambda }_1}\left(\frac{n_3}{n_2}\right)t$
4. $\frac{2\pi n_1}{{\lambda }_1}(n_3-n_2)t$

Q. A parallel monochromatic beam of light is incident normally on a narrow slit . A diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam.At the first minimum of the diffraction pattern, the phase difference between the rays from the two edges of the slit is

Q.

The orange light of wavelength$6000\times {10}^{-10}\mathrm{m}$ illuminates a single slit of width$0·6\times {10}^{-4}\mathrm{m}$. The maximum possible number of diffraction minima produced on both sides of the central maximum is?

Q. When the diffraction pattern from a certain slit illuminated with laser light (lambda = 6330 angstrom) is projected on a screen 150cmfrom the slit, the second minima on each side are seperated by 8cm. This tells us that 1-the slit is approximately 0.005cm wide 2-the slit is approximately 0.05cm wide 3-a/lambda = 7.5 approx. 4-a/lamda= 750 where a is slit width

Q. 2In Fraunhofer diffraction, the wavelength of light incident normally on the slit iswhere d is the width of the slit. What will be the number of bright fringes formed onan infinitely extended screen placed at any distance from the slit.

Q. A parallel beam of light of wavelength $500\text{nm}$ is incident at an angle ${30}^{\circ }$ with the normal to the slit plane in a Young's double slit experiment. The intensity due to each slit is $I_0$. Point $O$ is equidistant from $S_1$ and $S_2$. The distance between slits is $1\text{mm}$. Choose the correct statement.

1. The intensity at $O$ is zero.
2. The intensity at $O$ is $4I_0$.
3. The intensity at $O$ is $2I_0$.
4. The intensity at $O$ is $I_0/2$.

Q.

Angular width (b) of central maximum of a diffraction pattern on a single slit does not depend upon

[DCE 2000; 01]

1. Width of the slit

2. Frequency of light used

3. Distance between slit and source

4. Wavelength of light used

Q. width of slit diffraction such that 20 maxima of double slit experiment are obtained within the central maxima of diffraction pattern is?

Q. 30. Two slits are separated by 0.32 mm. A beam of 500 nm light strikes the slits producing an interference pattern. Determine the number of maxima observed in the angular range of -30^°

Q. For the oblique incidence and complete absorption, if angle $\theta$ is increased then radiation pressure -

1. also increases.
2. decreases.
3. remains constant.
4. None of these

Q.

In deriving the single slit diffraction pattern, it was stated that the intensity is zero at angles of nλ/a. Justify this by suitably dividing the slit to bring out the cancellation.

Q. A parallel monochromatic beam of light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam. At the first minimum of the diffraction pattern, the phase difference between the rays coming from the edges of the slit is.

1. $0$
2. $\frac{\pi }{2}$
3. $\pi$
4. $2\pi$

Q. 75. Two light rays having the same wavelength lambda in vacuum are in phase initially. Then the first ray travels a path L1 throgh a medium of refractive index n1 while the second ray travels a path of length L2 through a medium of refractive index n2. The two waves are then combined to produce interference. The phase difference between the two waves is?

Q. What is the graph of i and r?, where i is the incident ray and r is the refraction ray?