The wavelength of electromagnetic radiation is 900nm. Find its frequency
Answers
Answer:
Electromagnetic waves are categorized according to their frequency f or, equivalently, according to their wavelength λ = c/f. Visible light has a wavelength range from ~400 nm to ~700 nm. Violet light has a wavelength of ~400 nm, and a frequency of ~7.5*1014 Hz. Red light has a wavelength of ~700 nm, and a frequency of ~4.3*1014 Hz.
the visible EM spectrum
Visible light makes up just a small part of the full electromagnetic spectrum. Electromagnetic waves with shorter wavelengths and higher frequencies include ultraviolet light, X-rays, and gamma rays. Electromagnetic waves with longer wavelengths and lower frequencies include infrared light, microwaves, and radio and television waves.
Type of Radiation Frequency Range (Hz) Wavelength Range
gamma-rays 1020 - 1024 < 10-12 m
x-rays 1017 - 1020 1 nm - 1 pm
ultraviolet 1015 - 1017 400 nm - 1 nm
visible 4 - 7.5*1014 750 nm - 400 nm
near-infrared 1*1014 - 4*1014 2.5 μm - 750 nm
infrared 1013 - 1014 25 μm - 2.5 μm
microwaves 3*1011 - 1013 1 mm - 25 μm
radio waves < 3*1011 > 1 mm
image
Problem:
Two microwave frequencies are authorized for use in microwave ovens, 900 and 2560 MHz. Calculate the wavelength of each.
Solution:
Reasoning:
For all electromagnetic waves in free space λf = c.
Details of the calculation:
λ = c/f.
f = 900*106/s, λ = (1/3) m
f = 2560*106/s, λ = 11.7 cm.
Problem:
Distances in space are often quoted in units of light years, the distance light travels in one year.
(a) How many meters is a light year?
(b) How many meters is it to Andromeda, the nearest large galaxy, given that it is 2.54*106 light years away?
(c) The most distant galaxy yet discovered is 12*109 light years away. How far is this in meters?
Solution:
Reasoning:
All electromagnetic waves in free have speed c.
Details of the calculation:
(a) 1 light year (ly) = distance light travels in one year
= (3*108 m/s)*(365*24*3600 s) = 9.46*1015 m.
(b) The distance to Andromeda is 2.54*106 ly * 9.46*1015 m/ly = 2.4*1022 m.
(c) The distance to this galaxy is 12*109 ly * 9.46*1015 m/ly = 1.14*1026 m.