Lenses
Chapter 7: Lenses
Top questions
See all →- An object kept 60 cm from a lens gives a virtual image 20 cm in front of the lens. Answer: focal length = −30 cm; it is a diverging (concave) lens. Using the Cartesian sign convention, the object is on the left: u = -60 cm.... 1
- Three lenses having power 2, 2.5 and 1.7 D are kept touching in a row. What is the total power of the lens combination? Answer: 6.2 D When thin lenses are kept in contact, the power of the combination is the sum of their individual powers: P = P₁ + P₂ + P₃ = 2... 1
- 5 cm high object is placed at a distance of 25 cm from a converging lens of focal length of 10 cm. Answer: the image is 16.7 cm behind the lens, 3.33 cm tall, real, inverted and diminished. Using the Cartesian sign convention: u = -25 cm,... 1
- Doctor has prescribed a lens having power +1.5 D. What will be the focal length of the lens? What is the type of the lens and what must be the defect of vision? Given: Power of lens, P = +1.5 D, f=? Now, focal length of lens, f=1/P =1/(+1.5D) =10/15 m =+0.67 m P is positive, This shows the lens is co... 1
- What is the function of iris and the muscles connected to the lens in human eye? Function of Iris: The iris is a muscular diaphragm that controls the size of the pupil, which, in turn, controls the amount of light enterin... 1
- Distinguish between b. Concave lens and Convex Lens Concave lens Convex lens It is a diverging lens because it diverges the rays falling on it. It is a converging lens because it converges the... 1