In long range transmission, why micro waves are better carrier than radio waves?
Answer
In long range transmission, micro waves are better carrier than radio waves because their wavelength is very less as compared to radio waves. Due to this, during obstruction, they suffer minimum deviation and can be sent directly towards the aim.
Frequency of oscillation of electric field vector of any electromagnetic wave is $5 \times 10^{14} Hz$. What is the frequency of oscillation of corresponding magnetic field? To which part of electromagnetic spectrum is it associated?
A plane electromagnetic wave is travelling along Z-axis in vacuum. What can you say about the electric field and magnetic field vectors?
Answer
Electric field vector E and magnetic field vector B are perpendicular to the direction of propagation of wave and are also mutually perpendicular to each other. Since here the wave is travelling along the Z-axis, so vectors E and B are in the plane X-Y and mutually perpendicular to each other.
What are the main sources of electro- magnetic waves?
Answer
Electric field $\vec{E}$ is produced due to change in magnetic field $\vec{B}$ with time and similarly, magnetic field $\vec{B}$ is produced due to change in electric field $\vec{E}$ with time. In this way, change of these field vectors with time works as a source for each other. Hence the main sources of electromagnetic waves are magnetic field $\vec{B}$ and electric field $\vec{E}$.
Write mathematical expression for Ampere- Maxwell's law.
Answer
$\oint \overrightarrow{ B } \cdot \overrightarrow{d l}=\mu_0\left( I _c+ I _d\right)$where displacement current $I _d=\epsilon_0\left(\frac{d \phi_{ E }}{d t}\right)$ and $I _c=$ conduction current.
(a) In space, magnitude of electric field vector (E) at any point is $9.3 V / m$. Calculate the magnitude of magnetic field vector (B) at this point. (b) Out of ultraviolet, infrared and X-rays, whose wavelength is maximum?
Write names of those radiations of electromagnetic radiations which are :(i) used in satellite communication (ii) used to study crystal structure (iii) produced as a result of decay of radioactive nucleus (iv) wavelength in between 350 nm and 770 nm (v) absorbed by the ozone layer (vi) produce extensive heating effect.
Write frequency range of the following electromagnetic radiations and state one use of each :(i) Micro wave (ii) Ultraviolet radiation(iii) Gamma rays.
Answer
(i) $1 \times 10^9 Hz$ to $3 \times 10^{11} Hz$ (In radar) (ii) $8 \times 10^{14} Hz$ to $1 \times 10^{16} Hz$ (In food conservation) (iii) $3 \times 10^{18} Hz$ to $3 \times 10^{22} Hz$ (In radio therapy)
Write the name of that part of electromagnetic spectrum with which electromagnetic waves of following wavelength associated. Write them in descending order of wavelength. (a) $\lambda_1$ : used in treatment of muscular strains (b) $\lambda_2$ : used in radio transmission (c) $\lambda_3$ : used to detect fracture in bones (d) $\lambda_4:$ are absorbed by ozone layer in the atmosphere
Find wavelength of electromagnetic wave of frequency $4 \times 10^9 Hz$ in vacuum. Write its two uses also.
Answer
$\lambda=\frac{c}{v}=\frac{3 \times 10^8 m / s }{4 \times 10^9 s^{-1}}=0.075 m$
This wavelength is of micro waves and its two uses are :(i) In radar system, (ii) In microwave oven.
Write principle for producing the electromagnetic waves.
Answer
Accelerated charge produces electric and magnetic fields which change both with time and place. These changeable electric and magnetic fields give rise to electromagnetic waves.