Explain Wien's law and why our eyes are sensitive only to visible rays?

Give examples for metals sensitive to UV rays and then for visible light.

Explain why (or how): (a) in a sound wave a displacement node is a pressure antinode and vice versa. (b) bats can ascertain distances, directions, nature, and sizes of the obstacles without any ..eyes... (c ) a violin note and sitar note may have the same frequency. yet we can distinguish between the two notes. (d) solids can support both longitudinal and transverse waves, but only longitudinal waves can propagate in gases, and (e ) the shape of a pulse gets distorted during propagation in a dispersive medium.

When all colours of visible light strikes the retina of our eye at the same time ,our brain perceives------

a. The small ozone layer on the top of the stratosphere is crucial for human survival. Why ? b. Where is the position of UV radiation in the electromagnetic spectrum ? c. Can you convert UV to visible radiation ? Explain. d. Which radiation is adjacent to UV to the higher frequency side of the electromagnetic spectrum ?

a. The far point of a myopic person is 80cm in front of the eye. What is the power of the lens required to enable him to see very distant object clearly ? b. In what way does the corrective lens help the above person ? Does the lens magnify very distant objects? Explain carefully. c. The above person profers to remove his spectacles while reading a book Explain why.

If we put a cardboard (say 20 cm xx 20 cm) between a light source and our eyes, we can't see the light. But when we put the same cardboard between a sound source and our ear, we hear the sound almost clearly, Explain.

a. The near point of a hypermetropic person is 75 cm from the eye. What is the power of the lens required to enable the person to read clearly a book held at 25 cm from the eye? b . In what way does the corrective lens help the above person? Does the lens magnify objects held near the eye ? c. The above person prefers to remove the spectacles with looking at the sky. Explain why .

Define pascal's law. Explain the application of pascal's law in our daily life.