Force, Work, Energy and Power — Physics STD 10 — Question

In an experiment of finding the refractive index of glass, if blue light is replaced by the red light, how will the refractive index of glass change? Give reason in support of your answer.

An electric bulb is marked '100 W, 250 V'. What information does this convey?

A bulb marked 12 V, 24 W operates on a 12 volt car battery for 20 minutes. Calculate:
(i) The current flowing through it, and
(ii) The energy liberated.

(a) Which of the following quality determines the loudness of a sound wave?
(i) wavelength (ii) frequency and (iii) amplitude
(b) How is loudness related to the quantity mentioned above in part(a)?

(a) Write a relationship between the angle of incidence and the angle of refraction for a given pair of media.
(b) When a ray of light enters from one medium to another medium having different optical density, it bends. Why does this phenomenon occur?
(c) Write a condition where it does not bend when entering a medium of different optical density.

A man raises a box of mass 50kg to a height of 2m in 20s, while another man raises the same box to the same height in 50s. Compare:
(i) the work done, and
(ii) the power developed by them.

State Fleming's left hand rule.

Explain how is the principle of echo used by
(a) The bat during its flight at night,
(b) The dolphin to locate small fish as its prey.

Give scientific reason for the following:
Passengers in a bus are pushed backward when it starts suddenly.