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
Give a reason for the following:
Long-distance radio broadcasts use short-wave bands. Why?
Name the electromagnetic radiations used for (a) water purification, and (b) eye surgery.
Name the radiations of wavelength just longer than 8 × 10-7m.
Give one use of ultraviolet radiation.
An electromagnetic wave has a frequency of 500 MHz and a wavelength of 60 cm Calculate the velocity of the wave.
Is it possible that in a Coolidge tube characteristic Lα X-rays are emitted but not Kα X-rays?
Moseley's Law for characteristic X-ray is √v = a(Z − b). Here,
X-ray incident on a material
(a) exerts a force on it
(b) transfers energy to it
(c) transfers momentum to it
(d) transfers impulse to it.
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.
An X-ray tube operates at 40 kV. Suppose the electron converts 70% of its energy into a photon at each collision. Find the lowest there wavelengths emitted from the tube. Neglect the energy imparted to the atom with which the electron collides.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
-
- Calculate the speed of the wave.
- Name the medium through which it is traveling.
Name the radiation of the electromagnetic spectrum which is used for the following:
For taking photographs of the sky during the night and foggy conditions . Give the frequency range
Name two sources of infrared radiation.
Choose the correct option.
How does the frequency of a beam of ultraviolet light change when it travels from air into glass?
The frequency of e. m waves which is best suited .to observed of radius 3 × 10–4 his of the order of
A radio can tune to any station in the 7.5 mHz to 12 MHz band. What is corresponding wave length band.
Given below in the left column are different modes of communication using the kinds of waves given in the right column.
| A. | Optical Fibre Communication |
P. | Ultrasound |
| B. | Radar | Q. | Infrared Light |
| C. | Sonar | R. | Microwaves |
| D. | Mobile Phones | S. | Radio Waves |
From the options given below, find the most appropriate match between entries in the left and the right column.
Which one of the following electromagnetic radiation has the least wavelength?
Identify the electromagnetic wave whose wavelength range is from about 10-3 m to about 10-1 m. Write one use of this.
In an atom X, electrons absorb the energy from an external source. This energy “excites” the electrons from a lower-energy level to a higher-energy level around the nucleus of the atom. When electrons return to the ground state, they emit photons.
The figure below is the energy level diagram of atom X with three energy levels, E1 = 0.00eV, E2 = 1.78eV and E3 = 2.95eV. The ground state is considered 0 eV for reference. The transition of electrons takes place between levels E1 and E2.
- What wavelength of radiation is needed to excite the atom to energy level E2 from E1?
- Suppose the external source has a power of 100 W. What would be the rate of photon emission?
