# Ray Optics And Optical Instruments

## In the case of refraction of light : a) Frequency changes b) Speed changes c) Wavelength changes

A
a is correct
B
b and c are correct
C
a, b, c are correct
D
a and b are correct
Medium
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## Two equi-convex lenses each of focal lengths 20 cm and refractive index 1.5 are placed in contact and space between them is filled with water of refractive index 4/3. The combination works as :

A
converging lens of focal length 50 cm.
B
diverging lens of focal length 15 cm
C
converging lens of focal length 15 cm
D
diverging lens of focal length 50 cm
Medium
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