A convex lens of focal length 20cm and a concave lens of focal length f are mounted coaxially 5cm apart. Parallel beam of light incident on the convex lens emerges from the concave lens as a parallel beam. Then, f in cm is

A convex lens of focal length 1.0m and a concave lens of focal length9.25m are 0.75m apart. A parallel beam of light is incident on the convex lens. The beam emerging after refraction from both lenses is

A convex lens of focal length 10cm and concave lens of focal length 20 cm are kept 5 cm apart. The focal length of the equivalent lens is

A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are joined together. The power of the combination will be

A convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined toghether. What will be their resulting power ?

A thin convex lens of focal length 10 cm and a thin concave lens of focal length 26.2 cm are in contact. The combination acts as

A convex lens of focal length 1 meter and a concave lens of focal length 0.25 meter are kept 0.75 meter apart. A parallel beam of light first passes throught the convex lens, then through the concave lens and comes to a focus 0.5 m away from the the concave lens.

A convex lens of focal length 1 meter and a concave lens fo focal length 0.25 meter and kept 0.75 meter apart. A parallel beam of light first passes through the ocnvex lens, then through the concave lens and comes to a focus 0.5m away from the concave lens.

A convex lens of focal length 25 cm and a concave lens of focal length 20 cm are mounted coaxially separated by a distance d cm . If the power of the combination is zero, d is equal to