9. In the diagram, the input is across the terminals A and C and the output is across B and D. Then the output is ?

8. A piece of copper and other of germanium are cooled from the room temperature to 80 K, then ?

7. Diamond is very hard because ?

6. Which one of the following is the weakest kind of bonding in solids ?

5. For an electronic valve, the plate current I and plate voltage V in the space charge limited region are related as ?

4. The depletion layer in the p−n junction region is caused by ?

3. When n-type semiconductor is heated _ ?

2. p − n junction is said to be forward biased, when ?

1. At absolute zero, Si acts as :

39. The Brewsters angle $i_b$ for an interface should be :

38. Assume that light of wavelength 600 nm is coming from a star. The limit of resolution of telescope whose objective has a diameter of 2 m is :

37. Angular width of the central maxima in the Fraunhofer diffraction for λ = 6000Å is $θ_0$. When the same slit is illuminated by another monochromatic light, the angular width decreases by 30%. The wavelength of this light is :

36. Unpolarised light is incident from air on a plane surface of a material of refractive index ’ μ ’. At a particular angle of incidence ’ i ’, it is found that the reflected and refracted rays are perpendicular to each other. Which of the following options is correct for this situation ?

35. Two Polaroids $P_1$ and $P_2$ are placed with their axis perpendicular to each other. Unpolarised light $I_0$ is incident on $P_1$. A third polaroid $P_3$ is kept in between $P_1$ and $P_2$ such that its axis makes an angle 45° with that of $P_1$. The intensity of transmitted light through $P_2$ is ?

34. The ratio of resolving powers of an optical microscope for two wavelengths λ1 = 4000Å and λ2 = 6000Å is ?

33. In a diffraction pattern due to a single slit of width ’ a ’, the first minimum is observed at an angle 30° when light of wavelength 5000Å is incident on the slit. The first secondary maximum is observed at an angle of :

32. For a parallel beam of monochromatic light of wavelength ’ λ ’, diffraction is produced by a single slit whose width ’ a ’ is of the wavelength of the light. If ’ D ’ is the distance of the screen from the slit, the width of the central maxima will be :

31. At the first minimum adjacent to the central maximum of a single-slit diffraction pattern, the phase difference between the Huygen’s wavelet from the edge of the slit and the wavelet from the midpoint of the slit is :

30. A beam of light of λ = 600 nm from a dis- tant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is:

29. A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, which of the following statements is correct ?