An air bubble is formed inside water. Does it act as a converging lens or a diverging lens ?

What is the focal length of a convex lens of focal length 30cm in contact with a concave lens of focal length 20cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.

A point source S is placed at distance of 15 cm from a converging lens of focal length 10 cm . Where should a (i) concave mirror (ii) convex mirror of focal length 12 cm be placed so that real image is formed on object itself.

An air bubble inside water. The refractive index of water is 4/3 . At what distance from the air bubble should a point object be placed so as to form a real image at the same distance from the bubble:-

A combination is formed by keeping a convex lens in contact with a concave lens. If both have same focal length of value 25 cm, then power of combination is ...... D.

A point object O moves from the principal axis of a converging lens in a direction OP. I is the image of O, will move initially in the direction

Statement-1 : A balloon filled with CO_(2) gas acts as a coverging lens for a sound wave Statement-2 : Sound waves travel faster in air than in CO_(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 paralle 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)

Why does an air bubble form in water grow in size from bottom when it rises ?

Air bubble formed in liquid is considered as a sphere of air .initially ,bubble obtained acceleration is in upward direction and it is rising in liquid why ?