Calculate Focal Length

Calculate the focal length of a spherical mirror if radius of curvature is 20cm

• 20cm

• 10cm

• 15cm

• At infinity

Calculate the focal length of a lens with a power of +2.5 diopters.

• 0.4 m

• 0.5 m

• 0.2 m

• 0.25 m

A concave mirror has a focal length of 15 cm. What is the radius of curvature?

• 15 cm

• 30 cm

• 7.5 cm

• 10 cm

If the focal length of a convex lens is 25 cm, what is its power?

• +4 diopters

• +2 diopters

• +3 diopters

• +1 diopter

A lens has a focal length of -20 cm. What type of lens is it?

• Convex lens

• Concave lens

• Biconvex lens

• Plano-convex lens

Calculate the focal length of a mirror if the object distance is 30 cm and the image distance is 60 cm.

• 20 cm

• 15 cm

• 10 cm

• 30 cm

A lens forms an image at 50 cm when an object is placed at 100 cm. What is the focal length of the lens?

• 33.3 cm

• 25 cm

• 50 cm

• 20 cm

The focal length of a lens is 10 cm. What is the power of the lens?

• +10 diopters

• +5 diopters

• +2 diopters

• +1 diopter

A concave mirror has a radius of curvature of 40 cm. What is its focal length?

• 40 cm

• 20 cm

• 10 cm

• 30 cm

If a lens has a power of -3 diopters, what is its focal length?

• -0.33 m

• -0.5 m

• -0.25 m

• -0.2 m