20. In a Young’s double slit experiment, if there is no initial phase difference between the light from the two slits, a point on the screen corresponding to the fifth minimum has path difference ?

19. In Young’s double slit experiment the separation d between the slits is 2 mm, the wavelength λ of the light used is 5896Å and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is 0.20°. To increase the fringe angular width to 0.21° (with same λ and D) the separation between the slits needs to be changed to ?

18. Young’s double slit experiment is first performed in air and then in a medium other than air. It is found that $8^{th}$ bright fringe in the medium lies where $5^{th}$ dark fringe lies in air. The refractive index of the medium is nearly ?

17. The intensity at the maximum in a Young’s double slit experiment is $I_0$. Distance between two slits is d = 5λ, where λ is the wavelength of light used in the experiment. What will be the intensity in front of one of the slits on the screen placed at a distance D = 10 d ?

16. In a double slit experiment, the two slits are 1 mm apart and the screen is placed 1 m away. A monochromatic light wavelength 500 nm is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern ?

15. Two slits in Young’s experiment have widths in the ratio 1 : 25. The ratio of intensity at the maxima and minima in the interference pattern, $I_{max}$⁄$I_{min}$ is :

14. In the Young’s double-slit experiment, the intensity of light at a point on the screen where the path difference is λ is K, ( λ being the wave length of light used). The intensity at a point where the path difference is λ/4, will be :

13. In Young’s double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths $λ_1$ = 12000Å and $λ_2$ = 10000Å. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other ?

12. In Young’s double slit experiment the distance between the slits and the screen is doubled. The separation between the slits is reduced to half. As a result the fringe width :

11. In Young’s double slit experiment carried out with light of wavelength (λ) = 5000Å , the distance between the slits is 0.2 mm and the screen is at 200 cm from the slits. The central maximum is at x = 0. The third maximum (taking the central maximum as zeroth maximum) will be at x equal to ?

10. If yellow light emitted by sodium lamp in Young’s double slit experiment is replaced by a monochromatic blue light of the same intensity :

9. In Young’s experiment, two coherent sources are placed 0.90 mm apart and fringe are observed one metre away. If it produces second dark fringe at a distance of 1 mm from central fringe, the wavelength of monochromatic light used would be ?

8. The Young’s double slit experiment is performed with blue and with green light of wavelengths 4360Å and 5460Å respectively. If x is the distance of 4th maxima from the central one, then :

7. In Young’s double slit experiment, the fringe width is found to be 0.4 mm. If the whole apparatus is immersed in water of refractive index 4⁄3 , without disturbing the geometrical arrangement, the new fringe width will be ?

6. The periodic waves of intensities I1 and I2 pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is:

5. Colours appear on a thin soap film and on soap bubbles due to the phenomenon of ?

4. Interference was observed in interference chamber where air was present, now the chamber is evacuated, and if the same light is used, a careful observer will see ?

3. Ratio of intensities of two waves are given by 4 : 1. Then the ratio of the amplitudes of the two waves is ?

2. Interference is possible in ?

1. Which one of the following phenomena is not explained by Huygens construction of wavefront?