Two converging lenses of focal lengths `f_(1)=10cm` and `f_(2)=20cm` are placed at some separation. A parallel beam of light is incident on first lens. Then,

A convex lens of focal length 100 cm and a concave lens of focal length 10 cm are placed coaxialiy at a separation of 90 cm. If a parallel beam of light is incident on convex lens, then after passing through the two lenses the beam

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 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

Two thin lenses of focal length f_1 and f_2 are placed in contant .The focal length of the composite lens will be

In the figure shown a converging lens and a diverging lens of focal lengths 20cm and -5cm respectively are separated by a distance such that a paralel beam of light of intensity 100 watt//m^(2) incident on the converging lens comes out as parallel beam from the diverging lens. Find the intensity of the outgoing beam in watt//m^(2)

In the figure shown a converging lens and a diverging lens of focal lengths 20cm and -5cm respectively are separated by a distance such that a paralel beam of light of intensity 100 watt//m^(2) incident on the converging lens comes out as parallel beam from the diverging lens. Find the intensity of the outgoing beam in watt//m^(2)