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

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.

Use Lenz’s law to determine the direction of induced current in the situation described by the figure:

A wire of irregular shape turning into a circular shape.

What physical quantity is the same for X-rays of wavelength 10⁻¹⁰ m, red light of wavelength 6800 Å and radiowaves of wavelength 500 m?

A plane electromagnetic wave travels in vacuum along z-direction. What can you say about the directions of its electric and magnetic field vectors? If the frequency of the wave is 30 MHz, what is its wavelength?

A radio can tune in to any station in the 7.5 MHz to 12 MHz band. What is the corresponding wavelength band?

The terminology of different parts of the electromagnetic spectrum is given in the text. Use the formula E = hv (for energy of a quantum of radiation: photon) and obtain the photon energy in units of eV for different parts of the electromagnetic spectrum. In what way are the different scales of photon energies that you obtain related to the sources of electromagnetic radiation?

Use the formula λ_m T= 0.29 cm K to obtain the characteristic temperature ranges for different parts of the electromagnetic spectrum. What do the numbers that you obtain tell you?

Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.

(a) 21 cm (wavelength emitted by atomic hydrogen in interstellar space).

(b) 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).

(c) 2.7 K [temperature associated with the isotropic radiation filling all space-thought to be a relic of the ‘big-bang’ origin of the universe].

(d) 5890 Å - 5896 Å [double lines of sodium]

(e) 14.4 keV [energy of a particular transition in ⁵⁷Fe nucleus associated with a famous high resolution spectroscopic method (Mössbauer spectroscopy)].