A parallel beam of monochromatic light falls on a combination of a convex lens and a concave lens of focal - Physics - Ray Optics And Optical Instruments

Question

A parallel beam of monochromatic light falls on a combination of a
convex lens and a concave lens of focal length 15 centimetre and 5
centimetre respectively what is the distance between the two lenses
to obtain a parallel beam of light from the concave lens?

Vishes Rao · Answer

Use formula for two lens system here, the effective Focal length of
such system is
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A parallel beam of monochromatic light falls on a combination of a convex lens and a concave lens of focal length 15 centimetre and 5 centimetre respectively .what is the distance between the two lenses to obtain a parallel beam of light from the concave lens?