EASY
10th CBSE
IMPORTANT
Earn 100

A swimming pool appears less deep than it actually is due to a phenomenon called reflection.

50% studentsanswered this correctly

Important Questions on Light - Reflection and Refraction

EASY
10th CBSE
IMPORTANT
Things always look smaller on viewing through a convex lens.
EASY
10th CBSE
IMPORTANT
A concave lens can concentrate sun's rays to a point and burn a hole in a piece of paper.
EASY
10th CBSE
IMPORTANT
Concave lenses are thinner in the middle than at the edges.
EASY
10th CBSE
IMPORTANT
The nature of lens having a power of + 1.5 D is convex.
EASY
10th CBSE
IMPORTANT
The nature of lens having a power of - 3.25 D is concave.
EASY
10th CBSE
IMPORTANT
The power of the lenses A, B and C are respectively.
HARD
10th CBSE
IMPORTANT

The degree of convergence or divergence of light rays achieved by a lens is expressed in terms of its power. The power, P of a lens is given by the relation,

P=1f

where, f is the focal length of the lens in metres.

Many optical instruments use a number of lenses. These lenses are combined to increase the magnification and sharpness of the images produced. The resultant or net power of the combination of lenses placed in contact with each other is given by the algebraic sum of the individual powers of each of the lenses. If the individual powers of two lenses are P1 and P2, the resultant power, P is given by

P=P1+P2

The focal length, f of the combination of two lenses of focal lengths f1 and f2 is given by

f=f1f2f1+f2

Suppose you are given three lenses - A, B and C with focal lengths 10 cm, 20 cm and 30 cmA and B are convex lenses whereas C is a concave lens. The three lenses are kept in contact with each other.

On the basis of the above information and what you have studied in the course, answer the following question:

The focal length of the combination of lenses is

HARD
10th CBSE
IMPORTANT

The degree of convergence or divergence of light rays achieved by a lens is expressed in terms of its power. The power, P of a lens is given by the relation,
P=1f
where, f is the focal length of the lens in metres.
Many optical instruments use a number of lenses. These lenses are combined to increase the magnification and sharpness of the images produced. The resultant or net power of the combination of lenses placed in contact with each other is given by the algebraic sum of the individual powers of each of the lenses. If the individual powers of two lenses are P1 and P2, the resultant power, P is given by
P=P1+P2
The focal length, f of the combination of two lenses of focal lengths f1 and f2 is given by
f=f1f2f1+f2
Suppose you are given three lenses - A, B and C with focal lengths 10 cm, 20 cm and 30 cmA and B are convex lenses whereas C is a concave lens. The three lenses are kept in contact with each other.
On the basis of the above information and what you have studied in the course, answer the following question:

The power of the combination of lenses is