Question

A biconvex lens made of glass of refractive index 1.5 has radius of currature of both of its surfaces as 40cm. Calculate the (i) power and (ii) focal length of the lens. Also find out the change in the focal length of the lens when it is submerged in water.

Answer 1

Answer:

Focal length =1/f=1/v-1/u

Power =1/f u get

Sorry can't help you with submerged in water

Answer 2

Answer:

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Explanation:

If we talk About KINETIC ENERGY ――

Kinetic energy of the particle of mass m is,

K = ½ m [ω√a2 – y2]2

Kinetic energy of the particle of mass m is,

K = ½ m [ω√a2 – y2]2

Potential energy

From definition of SHM F = –ky the work done by the force during the small displacement dy is dW = −F.dy = −(−ky) dy = ky dy

Total energy, E = K+U

= ½ mω2 (a2 – y2) + ½ mω2y2

= ½ mω2a2

So,

Thus we find that the total energy of a particle executing simple harmonic motion is ½ mω2a2. The displacement is half of the amplitude, K = ¾ E and U = ¼ E. K and U are in the ratio 3 : 1.

E = K+U = ½ mω2a2

At any other position the energy is partly kinetic and partly potential.

This shows that the particle executing SHM obeys the law of conservation of energy.