CBSE Physics Ray Optics and Optical Instruments Test 2 Online

1. A convex lens and a concave lens, each having same focal length of 25 cm, are put in contact to from a combination of lenses. The power in diopters of the combination is ?

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

3. Colours of thin soap bubbles are due to ?

4. Which of the following phenomena exhibits particles nature of light ?

5. Light enters at an angle of incidence in a transparent rod of refractive index. For what value of the refractive index of the material of the rod the light once entered into it will not leave it through its lateral face whatsoever be the value of angle of incidence ?

6. The wavelength of light of frequency 100 Hz is ?

7. A telescope has an objective lens of 10 cm diameter and is situated at a distance of one kilometer from two objects, which can be resolved buy the telescope, when the mean wavelength of light is 500 A°, is of the order of ?

8. A man is 6 ft tall. In order to see his entire image, he requires a plane mirror of minimum length equal to ?

9. The refractive index of the material of a prism is √2 and its refracting angle is 30°. One of the refracting surfaces of the prism is made a mirror inwards. A beam of monochromatic light entering the prism from the other face will retrace its path after reflection from the mirrored surface, if its angle of incidence on the prism is ?

10. Rainbows are formed by ?

11. A planoconvex 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 ?

12. 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 ?

13. Two thin lenses of focal lengths f₁ and f₂ are in contact and coaxial. The power of the combination is ?

14. A transparent cube contains a small air bubble. It apparent distance is 2 cm when seen through one face and 5 cm when seen through other face. If the refractive index of the material of the cube is 1.5, the real length of the edge of cube must be ?

15. A convex lens is dipped in a liquid whose refractive index is equal to the refractive index of the lens. Then its focal length will ?