Two converging lenses of unequal focal lengths can be used to reduce the aperture of a parallel beam of light without loosing the energy of the light. This increases the intensity. Describe how the converging lenses should be placed to do this.

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,

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)

A convex lens of focal length 1.0m and a concave lens of focal length 0.25m 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 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 perfectly reflecting solid hemisphere of radius R is placed in the path of a parallel beam of light of large aperture. If the beam carrries an intensity l, find the force exerted by the beam on the hemisphere.

Two converging lenses of the same focal length f are separated by a distance 2f. The axis of the second lens is inclined at angle theta=60^@ with respect to the axis of the first lens. A parallel paraxial beam of light is incident from left side of the lens. Find the coordinates of the final image with respect to the origin of the first lens.

Consider a 'beam expander' which consists of two converging lenses of focal length 40 cm and 100 cm having a common optical axis. A laser beam of diameter 4 mm is incident on the 40 cm focal length lens. Then what is the diameter of the final beam (see figure)

Two converging glass lenses A and B have focal lengths in the ratio 2:1 . The radius of curvature of first surface of lens A is 1/4 th of the second surface where as the radius of curvature of first surface of lens B is twice that of second surface. Then the ratio between the radii of the first surfaces of A and B is

Figure given below shows a beam of light converging at point P. When a concave lens of focal length 16cm is introduced in the path of the beam at a place O shown by dotted line such that OP becomes the axis of the lens, the beam converges at a distance x from the lens. The value x will be equal to

L is a lens such that a parallel beam of light I ncident on it, after refraction, converges to a point at a distance x from it and M is a mirror such that a parallel lbeam of light incident on it, after reflection, converges to a point at a distance y from it. Now the lens L and mirror M are placed at a distan 2(x+y) from each other. An object of size 2 cm is kept infront of lens at a distance 2x from it. Find the nature, position , and size of the image that willl be seen by an observer looking toward the mirror through the lens.