Ray Optics and Optical Instruments - Online Test

Q1. The equi-convex lens, show in the figure, has a focal length ƒ. What will be the focal length of each half if the lens it cut along AB?

Answer : Option A
Explaination / Solution:
No Explaination.


Q2. A person can see clearly only up to a distance of 30 cm. He wants to read a book placed at a distance of 50 cm from his eyes. What is the power of the lens he requires for his spectacles?
Answer : Option A
Explaination / Solution:
No Explaination.


Q3. A person with defective eyesight is unable to see objects clearly nearer than 1.5 m. He wants to read a book placed at a distance of 30 cm from his eyes. Find the power of the lens he requires for his spectacles
Answer : Option B
Explaination / Solution:
No Explaination.


Q4. A plano-convex lens is made of glass of refractive index 1.5.The focal length ƒ of the lens and radius of curvature R of its curved face are related as
Answer : Option A
Explaination / Solution:
No Explaination.


Q5.
A thin convergent glass lens ( = 1.5 ) has a power of + 5.0 D. When this lens is immersed in a liquid of refractive index  it acts as a divergent lens of focal length 100 cm. The value of must be

Answer : Option D
Explaination / Solution:
No Explaination.


Q6. What is the relation between refractive indices  1 and  2 if the behavior of light rays is as shown in the following figure?

Answer : Option B
Explaination / Solution:
No Explaination.


Q7. A lens forms a sharp image on a screen. On inserting a parallel sided glass slab between the lens and the screen, it is found necessary to move the screen a distance d away from the lens in order to focus the image sharply. If the refractive index of glass relative to air is μ, the thickness of the glass slab is given by
Answer : Option C
Explaination / Solution:
No Explaination.


Q8. An object and a screen are mounted on an optical bench and a converging lens is placed between them so that a sharp image is received on the screen. The linear magnification of the image is 2.5. The lens is now moved 30 cm nearer the screen and a sharp image is again formed on the screen. The focal length of the lens is
Answer : Option C
Explaination / Solution:
No Explaination.


Q9. A lamp and a screen are set up 100 cm apart and a convex lens is placed between them. The two positions of the lens forming real images on the screen are 40 cm apart. What is the focal length of the lens ?
Answer : Option B
Explaination / Solution:
No Explaination.


Q10. A convex lens forms a real image of an object on a screen; the magnification of the image being 3/2. The object and the screen are kept fixed and the lens is moved through a distance of 16 cm when a sharp image is again formed on the screen; the magnification now being 2/3. What is the focal length of the lens?
Answer : Option B
Explaination / Solution:
No Explaination.