The biological importance of the ozone layer is:
1. | it stops ultraviolet rays. |
2. | ozone layer reduces the greenhouse effect. |
3. | ozone layer reflects radio waves. |
4. | ozone layer controls \(\mathrm{O}_2 / \mathrm{H}_2\) ratio in the atmosphere. |
The velocity of electromagnetic waves is parallel to:
1.
2.
3.
4.
If the frequency of an EM wave is \(10\) MHz, then its wavelength is:
1. \(30\) m
2. \(300\) m
3. \(3\) m
4. none of the above
What is the cause of “Greenhouse effect”?
1. Infra-red rays
2. Ultraviolet rays
3. \(X\text-\)rays
4. Radio waves
Which of the following has the minimum wavelength?
1. \(X\text-\)rays
2. Ultraviolet rays
3. \(\gamma\text-\)rays
4. Cosmic rays
If \(\lambda_{v}, \lambda_{x},\) and \(\lambda_{m}\) represent the wavelengths of visible light, \(x\text-\)rays and microwaves respectively, then:
1. \( \lambda_{m}>\lambda_{x}>\lambda_{v} \)
2. \( \lambda_{v}>\lambda_{m}>\lambda_{x } \)
3. \( \lambda_{v}>\lambda_{x}>\lambda_{m }\)
4. \(\lambda_{m}>\lambda_{v}>\lambda_{x}\)
A capacitor of capacitance \(C\) is connected across an AC source of voltage \(V\), given by;
\(V=V_0 \sin \omega t\)
The displacement current between the plates of the capacitor would then be given by:
1. \( I_d=\frac{V_0}{\omega C} \sin \omega t \)
2. \( I_d=V_0 \omega C \sin \omega t \)
3. \( I_d=V_0 \omega C \cos \omega t \)
4. \( I_d=\frac{V_0}{\omega C} \cos \omega t\)
1. | \( b>a>c \) | 2. | \( a>b>c \) |
3. | \( c>b>a \) | 4. | \( a>c>b\) |
The electric field of an electromagnetic wave in free space is given by –
, 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?
1. (a) and (b)
2. (b) and (c)
3. (c) and (d)
4. (a) and (c)