Geometrical Optics Problems - Physics 11th - Chapter 10 - Sindh Textbook Board (stb problems)

 

GEOMETRICAL OPTICS

(PROBLEMS)

Problem 10.1. An object 4 cm tall is placed near the axis of a thin converging lens. If the focal length of the lens is 25 cm, where will the image be formed and what will be the size of the image? Sketch the principal ray diagram.

Problem 10.2. A convex lens has a focal length of 10 cm. Determine the image distances when an object is placed at the following distances from the lens.

(50 cm, 20 cm, 15 cm, 10 cm and 5 cm).

Problem 10.3. Two converging lenses of focal lengths 40 cm and 50 cm are placed in contact. What is the focal length of this lens combination? What is the power of the combination in diopters?

Problem 10.4. A converging lens of focal length 20 cm is placed in front of a converging lens of focal length 4 cm. What is the distance between the lenses if parallel rays entering the first lens leave the second lens as parallel rays?

Problem 10.5. A parallel light beam is diverged by a concave lens of focal length -12.5cm and then made parallel once more by a convex lens of focal length 50cm. How far are the two lenses apart.

Problem 10.6. Two lenses are in contact, a converging one of focal length 30cm and a diverging one of focal length 10cm. What is the focal length and power of the combination?

Problem 10.7. Moon light passes through a converging lens of focal length 19 cm, which is 20.5 cm from a second converging lens of focal length 2 cm. Where is the image of the moon produced by the lens combination?

Problem 10.8. Find the distance at which an object should be placed in front of a convex lens of focal length 10 cm to obtain an image of double its size?

Problem 10.9. A compound microscope has a 12 mm focal length objective and a 75 mm focal length eye piece, and the two lenses are mounted 200 mm apart. If the final image is 225 mm from the eye piece, what is the magnification produced?

Problem 10.10. An astronomical telescope of angular magnification 1000 has an objective of 15 m focal length. What is the focal length of the eye piece?

Problem 10.11. A Galilean telescope has an objective of 120 mm focal length and an eye piece of 50 mm focal length. If the image seen by the eye is 300 mm from the eye piece, what is angular magnification?

Problem 10.12. A compound microscope has an objective with a focal length of 10 mm and a tube 100 mm long. An image is produced 250 mm from the eye piece when the object is 12 mm from the objective. What is the angular magnification?

Problem 10.13. A converging lens of 4 dioptres is combined with a diverging lens of −2 dioptres. Find the power and focal length of the combination?

Problem 10.14. A convex lens forms image of an object on a fixed screen 20 cm from the lens. On moving the lens 60 cm towards the object, the image is again formed on the screen. What is the focal length of the lens?

Problem 10.15. Two converging lenses are 25 cm part. Focal length of each is 10 cm. An object is placed in front of one lens at 50 cm. Find the distance between the object and the final image?