Echoes and Vibrations of Sound — Physics STD 10 — Question

State Ohm's law. Is it always true?

The temperature of the surrounding starts falling when ice in a frozen lake starts melting. Give reason.

Define the terms velocity and wavelength applied to sound wave and state the relation between velocity, frequency and wavelength.

How do bats avoid obstacles in their way, when in flight?

A coin is places at the bottom of a beaker containing water (refractive index = 4/3) to a depth of 12 cm. By what height the coin appears to be raised when seen from vertically above?

How are the e.m.f in the primary and secondary coils of a transformer related with the number of turns in these coils?

Draw a diagram, properly labelled, to illustrate the use of a total reflecting prism (a right-angled isosceles prism) to turn a ray of light through 180°. Name an instrument in which this device is used.

Draw another diagram to show how the colours of spectrum of white light can be combined to give the effect of white light.

Explain with the help of a diagram how does 'short circuiting' occur in an electric kettle.