Advertisements
Advertisements
प्रश्न
The magnetic field of a beam emerging from a filter facing a floodlight is given by B0 = 12 × 10–8 sin (1.20 × 107z – 3.60 × 1015t) T. What is the average intensity of the beam?
Advertisements
उत्तर
The standard equation of magnetic field can be expressed as B = B0 sin ωt.
We are given equation B = 12 × 10–8 sin (1.20 × 107z – 3.60 × 1015t) T.
On comparing this equation with standard equation, we get
B0 = 12 × 10–8 T
The average intensity of the beam
`I_(av) = 1/2 B_0^2/mu_0 * c = 1/2 xx ((12 xx 10^-8)^2 xx 3 xx 10^8)/(4pi xx 10^-7)`
= 1.71 W/m2
APPEARS IN
संबंधित प्रश्न
Why are microwaves considered suitable for radar systems used in aircraft navigation?
Use the formula λm 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?
Name the electromagnetic radiations used for (a) water purification, and (b) eye surgery.
Name the region beyond the violet end of the spectrum called.
What do you understand by the invisible spectrum?
Name the radiations of wavelength just longer than 8 × 10-7m.
Name three properties of ultraviolet radiations which are similar to visible light.
Name of physical quantity which remains same for microwaves of wavelength 1 mm and UV radiations of 1600 Å in vacuum.
Why is exposure to X-rays injurious to health but not exposure to visible light, when both are electromagnetic waves?
X-ray from a Coolidge tube is incident on a thin aluminium foil. The intensity of the X-ray transmitted by the foil is found to be I0. The heating current is increased to increase the temperature of the filament. The intensity of the X-ray transmitted by the foil will be
(a) zero
(b) < I0
(c) I0
(d) > I0
The Kβ X-rays from certain elements are given below. Draw a Moseley-type plot of √v versus Z for Kβ radiation.
| Element | Ne | P | Ca | Mn | Zn | Br |
| Energy (keV) | 0.858 | 2.14 | 4.02 | 6.51 | 9.57 | 13.3 |
Heat at the rate of 200 W is produced in an X-ray tube operating at 20 kV. Find the current in the circuit. Assume that only a small fraction of the kinetic energy of electrons is converted into X-rays.
The Kα X-rays of aluminium (Z = 13) and zinc (Z = 30) have wavelengths 887 pm and 146 pm respectively. Use Moseley's law √v = a(Z − b) to find the wavelengths of the Kα X-ray of iron (Z = 26).
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Name three radiations and their wavelength range which are invisible and beyond the violet end of the visible spectrum.
Answer briefly.
Give two uses of radio waves.
Solve the numerical problem.
Calculate the frequency in MHz of a radio wave of wavelength 250 m. Remember that the speed of all EM waves in a vacuum is 3.0 × 108 m/s.
Solve the numerical problem.
Calculate the wavelength in nm of an X-ray wave of frequency 2.0 × 1018 Hz.
The frequency of x-rays, y-rays and ultraviolet rays are respectively a, b and c. Then:-
Why does microwave oven heats up a food item containing water molecules most efficiently?
