Science (English Medium) Class 12 - CBSE Question Bank Solutions for Physics

Draw a sketch of a sinusoidal carrier wave along with a modulating signal and show how these are superimposed to obtain the resultant amplitude modulated wave

How are infrared waves produced?

What role dose infra-red radiation play in maintain the Earth’s warmth

What role dose infra-red radiation play in physical therapy?

A series LCR circuit is connected across an a.c. source of variable angular frequency 'ω'. Plot a graph showing variation of current 'i' as a function of 'ω' for two resistances R₁ and R₂ (R₁ > R₂).

Answer the following questions using this graph :

(a) In which case is the resonance sharper and why?

(b) In which case in the power dissipation more and why?

State Lenz's law. Illustrate, by giving an example, how this law helps in predicting the direction of the current in a loop in the presence of a changing magnetic flux.

Define the term 'intensity of radiation' in terms of photon picture of light.

How are side bands produced?

Identify the part of the electromagnetic spectrum which is suitable for radar system used in aircraft navigation.

Identify the part of the electromagnetic spectrum which is:

produced by bombarding a metal target by high speed electrons.

Name the parts of the electromagnetic spectrum which is

used to treat muscular strain.

Write in brief, how these waves can be produced.

Name the parts of the electromagnetic spectrum which is

used as a diagnostic tool in medicine.

Write in brief, how these waves can be produced.

The carrier wave is given by

C(t) = 2sin(8πt) volt.

The modulating signal is a square wave as shown. Find modulation index.

If the earth did not have atmosphere, would its average surface temperature be higher or lower than what it is now? Explain.

Describe a simple experiment (or activity) to show that the polarity of emf induced in a coil is always such that it tends to produce a current which opposes the change of magnetic flux that produces it.

To which part of electromagnetic spectrum does a wave of frequency 3 × 10¹³ Hz belong?

A voltage V = V₀ sin ωt is applied to a series LCR circuit. Derive the expression for the average power dissipated over a cycle. Under what condition (i) no power is dissipated even though the current flows through the circuit, (ii) maximum power is dissipated in the circuit?

To which part of the electromagnetic spectrum does a wave of frequency 5 × 10¹⁹ Hz belong?

To which part of the electromagnetic spectrum does a wave of frequency 5 × 10¹¹ Hz belong?

Predict the direction of induced current in the situation described by the following figure.