36. A body is located on a wall. Its image of equal size is to be obtained on a parallel wall with the help of a convex lens. The lens is placed at a distance ’ d ’ ahead of second wall, then the required focal length will be ?

35. The radius of curvature of a thin plano convex lens is 10 cm (of curved surface) and the refractive index is 1.5 . If the plane surface is silvered, then it behaves like a concave mirror of focal length ?

34. A plano-convex lens is made of material of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is ?

33. A luminous object is placed at a distance of 30 cm from the convex lens of focal length 20 cm. On the other side of the lens, at what distance from the lens a convex mirror of radius of curvature 10 cm be placed in order to have an upright image of the object coincident with it ?

32. The focal length of converging lens is measured for violet, green and red colours. It is respectively $f_v, f_g, f_r$. We will get ?

31. A convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together. What will be their resulting power ?

30. If $f_V$ and $f_R$ are the focal lengths of a convex lens for violet and red light respectively and $F_V$ and $F_R$ are the focal lengths of concave lens for violet and red light respectively, then we have ?

29. An achromatic combination of lenses is formed by joining ?

28. A lens is placed between a source of light and a wall. It forms images of area $A_1$ and $A_2$ on the wall for its two different positions. The area of the source of light is ?

27. Focal length of a convex lens will be maximum for ?

26. Focal length of a convex lens of refractive index 1.5 is 2 cm. Focal length of the lens when immersed in a liquid of refractive index of 1.25 will be ?

25. In total internal reflection when the angle of incidence is equal to the critical angle for the pair of media in contact, what will be angle of refraction ?

24. Which of the following is not due to total internal reflection ?

23. A ray of light travelling in a transparent medium of refractive index μ, falls on a surface separating the medium from air at an angle of incidence of 45° .For which of the following value of μ the ray can undergo total internal reflection ?

22. The frequency of a light wave in a material is 2 × 10¹⁴ Hz and wavelength is 5000A ̊ . The refractive index of material will be ?

21. A small coin is resting on the bottom of a beaker filled with liquid. A ray of light from the coin travels upto the surface of the liquid and moves along its surface. How fast is the light travelling in the liquid ?

21. A small coin is resting on the bottom of a beaker filled with liquid. A ray of light from the coin travels upto the surface of the liquid and moves along its surface. How fast is the light travelling in the liquid ?

20. A beam of light composed of red and green rays is incident obliquely at a point on the face of rectangular glass slab. When coming out on the opposite parallel face, the red and green rays emerge from ?

19. A light ray falls on a rectangular glass slab as shown. The index of refraction of the glass, if total internal reflection is to occur at the vertical face, is ?

19. A light ray falls on a rectangular glass slab as shown. The index of refraction of the glass, if total internal reflection is to occur at the vertical face, is ?

18. The reddish appearance of the sun at sunrise and sunset is due to ?

17. An air bubble in a glass slab (μ = 1.5) is 5 cm deep when viewed from one face and 2 cm deep when viewed from the opposite face. The thickness of the slab is ?