ICSE.X.PHYSICS. 5. REFRACTION THROUGH A LENS

A point object is placed at a distance of 12 cm from a convex lens on its principal axis. Its image is formed on the other side of the lens at a distance of 18 cm from the lens. Find the focal length of the lens.

• 7.2 cm

• 10 cm

• 15 cm

• 20 cm

An object 3 cm high is placed at a distance of 20 cm in front of a convex lens of focal length 12 cm. Find the position of the image formed.

• 30 cm.

• 25 cm.

• 15 cm.

• 10 cm.

A convex lens has a focal length of 20 cm. Find the distance from the lens where an object should be placed so that it forms an image at a distance of 40 cm on the other side of the lens.

• 40 cm.

• 10 cm.

• 30 cm.

• 60 cm.

An object 5 cm high is held 25 cm away from a converging lens of focal length 10 cm. Find the position and size of the image formed.

• 16.67 cm, 3.33 cm.

• 20 cm, 4 cm.

• 15 cm, 3 cm.

• 10 cm, 2 cm.

An object of size 3 cm is placed at a distance of 15 cm from a convex lens of focal length 10 cm. Find the size of the image formed.

• 6 cm.

• 3 cm.

• 9 cm.

• 12 cm.

A 10 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 30 cm. The distance of the object from the lens is 20 cm. Find the position of the image formed.

• 60 cm

• -60 cm

• 30 cm

• -30 cm

A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens?

• 30 cm.

• 20 cm.

• 25 cm.

• 35 cm.

A 8 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 25 cm. The distance of the object from the lens is 30 cm. Find the size of the image formed.

• 40 cm

• 10 cm

• 20 cm

• 30 cm

A 5 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. Find the size of the image formed.

• 10 cm

• 5 cm

• 15 cm

• 20 cm

A compound lens is made of two lenses in contact having powers +12.5 D and –2.5D. Find the focal length of the combination.

• 0.1 m.

• 0.2 m.

• 0.05 m.

• 0.5 m.