Advertisements
Advertisements
Question
Continuous X-rays are made to strike a tissue paper soaked with polluted water. The incoming X-rays excite the atoms of the sample by knocking out the electrons from the inner shells. Characteristic X-rays are analysed and the intensity is plotted against the wavelength. Assuming that only Kα intensities are detected, list the elements present in the sample from the plot. Use Moseley's equation v − (25 × 1014Hz)(Z − 1)2.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Advertisements
Solution
Given :-
`f = (25 × 10^14 "Hz") (Z − 1)^2`
`or c/lambda = 25 xx 10^14(Z - 1)^2`
(a) `(3 xx 10^8)/(78.9 xx 10^-12 xx 25 xx 10^14)` = `(Z - 1)^2`
or `(Z - 1)^2 = 0.001520 xx 10^6 = 1520`
`⇒ Z - 1 = 38.98`
`or Z = 39.98 = 40`
Thus , it is (Zr) .
(b) `(3 xx 10^8)/(146 xx 10^-12 xx 25 xx 10^14)` = `(Z - 1)^2`
`or (Z - 1)^2 = 0.00082219 xx 10^6`
`or Z - 1 = 28.669`
`or Z = 29.669 = 30`
Thus , it is (Zn).
(c) `(3 xx 10^8)/(158 xx 10^-12 xx 25 xx 10^14) = (Z - 1)^2`
`or (Z -1)^2 = 0.0007594 xx 10^4`
`or Z - 1 = 27.5559`
`or Z - 1 = 28.5589 = 29`
Thus , it is (Cu).
(d) `(3 xx 10^8)/(198 xx 10^-12 xx 25 xx 10^14) = (Z - 1)^2`
`or (Z - 1)^2 = 0.000606 xx 10^4`
`or Z-1 = 24.6162`
`or Z = 25.6162 = 26`
Thus , it is (Fe).
APPEARS IN
RELATED QUESTIONS
A plane electromagnetic wave travels in vacuum along z-direction. What can you say about the directions of its electric and magnetic field vectors? If the frequency of the wave is 30 MHz, what is its wavelength?
Give a reason for the following:
It is necessary to use satellites for long-distance TV transmission. Why?
Name the high energetic invisible electromagnetic waves which help in the study of the structure of crystals
What do you understand by the statement, "Electromagnetic waves transport momentum"?
What is the range of the wavelength of the following electromagnetic waves?
(A) Radio waves.
Moseley's Law for characteristic X-ray is √v = a(Z − b). Here,
Frequencies of Kα X-rays of different materials are measured. Which one of the graphs in the figure may represent the relation between the frequency v and the atomic number Z ?
The distance between the cathode (filament) and the target in an X-ray tube is 1.5 m. If the cutoff wavelength is 30 pm, find the electric field between the cathode and the target.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Arrange the following electromagnetic waves in increasing order of their frequencies (i.e. begin with the lowest frequency):
Visible light, y rays, X rays, microwaves, radio waves, infrared radiations, and ultraviolet radiation.
Name the part of the electromagnetic spectrum which is:
Produced by bombarding a metal target with high electrons.
Name two sources of infrared radiation.
Name the radiations used for the detection of fracture in bones.
A radio can tune to any station in the 7.5 mHz to 12 MHz band. What is corresponding wave length band.
If λv, λx and λm Am represents the wavelength of visible light, x-ray and microwaves respectively, then ______.
The electric field intensity produced by the radiations coming from 100 W bulb at a 3 m distance is E. The electric field intensity produced by the radiations coming from 50 W bulb at the same distance is ______.
The ratio of contributions made by the electric field and magnetic field components to the intensity of an EM wave is ______.
Electromagnetic waves of wavelengths λ1, λ2 and λ3 are used in a radar system, in water purifiers and in remote switches of TV, respectively.
- Identify the electromagnetic waves.
- Write one source for each of them.
Give any two uses of infrared waves.
Which one of the following electromagnetic radiation has the least wavelength?
