23538.Match List–I (Electromagnetic wave type) with List–II (its association/application) and select the correct option from the choices given below the lists :
| List – I | List – II | ||
|---|---|---|---|
| (a) | Infrared waves | (i) | To treat muscular strain |
| (b) | Radio waves | (ii) | For broadcasting |
| (c) | X–rays | (iii) | To detect fracture of bones |
| (d) | Ultraviolet rays | (iv) | Absorbed by the ozone layer of the atmosphere |
(i) (ii) (iv) (iii)
(iii) (ii) (i) (iv)
(i) (ii) (iii) (iv)
(iv) (iii) (ii) (i)
23539.A radar has a power of 1 kW and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. The maximum distance up to which it can detect object located on the surface of the earth(Radius of earth = 6.4 × 106 m) is :
80 km
16 km
40 km
64 km
23540.The electric and magnetic field of an electromagnetic wave are
in opposite phase and perpendicular to each other
in opposite phase and parallel to each other
in phase and perpendicular to each other
in phase and parallel to each other.
23541.Out of the following options which one can be used to produce a propagating electromagnetic wave?
A chargeless particle
An accelerating charge
A charge moving at constant velocity
A stationary charge
23542.A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the light at a distance of 1 m from the diode is
1.73 V/m
2.45 V/m
5.48 V/m
7.75 V/m
23543.Assertion : Television signals are received through sky–wave propagation.
Reason : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.
Reason : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.
both assertion and reason are true and reason is the correct explanation of assertion.
both assertion and reason are true but reason is not the correct explanation of assertion.
assertion is true but reason is false.
assertion and reason are false.
23544.Which of the following spectral series of hydrogen atom is lying in visible range of electromagnetic wave?
Paschen series
Pfund series
Lyman series
Balmer series
23545.Pick out the longest wavelength from the following types of radiations.
Blue light
Gamma rays
X–rays
Red light
23546.In electromagnetic spectrum, the frequencies of γ–rays, X–rays and ultraviolet rays are denoted by n1, n2 and n3 respectively then
n1 > n2 > n3
n1 < n2 < n3
n1 > n2 < n3
n1 < n2 > n3
23547.A plane electromagnetic wave of frequency 20 MHz travels through a space along x direction. If the electric field vector at a certain point in space is 6 V m–1, what is the magnetic field vector at that point?
2 × 10–8 T
1/2 × 10–8 T
2 T
1/2 T
23548.The electric field part of an electromagnetic wave in a medium is represented by $E_x = 0, E_y = 2.5\dfrac{N}{C}cos\left[\left(2\pi \times 10^6 \dfrac{rad}{s}\right)t – \left(\pi \times 10^{–2}\dfrac{rad}{m}\right)x\right], E_z = 0$. The wave is
Moving along –$x$ direction with frequency 106 Hz and wavelength 200 m
Moving along $y$ direction with frequency 2π × 106 Hz and wavelength 200 m
Moving along $x$ direction with frequency 106 Hz and wavelength 100 m
Moving along $x$ direction with frequency 106 Hz and wavelength 200 m
23549.An electromagnetic wave of frequency v = 3.0 MHz passes from vacuum into a dielectric medium with permittivity ε = 4.0. Then:
wavelength is doubled and frequency remains unchanged
wavelength is doubled and frequency becomes half
wavelength is halved and frequency remains unchanged
wavelength and frequency both remain unchanged
23550.During the propagation of electromagnetic waves in a medium
Electric energy density is half of the magnetic energy density.
Electric energy density is equal to the magnetic energy density.
Both electric and magnetic energy densities are zero.
Electric energy density is double of the magnetic energy density.
23551.The electric field of an electromagnetic wave in free space is given by $\overrightarrow{E} = 10cos(10^7t +kx)\hat{j} \;V/m$ where t and $x$ are in seconds and metres respectively. It can be inferred that
(a) The wavelength λ is 188.4 m
(b) The wave number k is 0.33 rad/m
(c) The wave amplitude is 10 V/m
(d) The wave is propagating along +$x$ direction
Which one of the following pairs of statements is correct?
(a) The wavelength λ is 188.4 m
(b) The wave number k is 0.33 rad/m
(c) The wave amplitude is 10 V/m
(d) The wave is propagating along +$x$ direction
Which one of the following pairs of statements is correct?
(c) & (d)
(a) and (b)
(b) & (c)
(a) & (c)
23552.The energy of the em waves is of the order of 15 keV. To which part of the spectrum does it belong?
γ–rays
X–rays
Infra–red rays
Ultraviolet rays