Question

The Atacama Large Millimetre Array (ALMA) can observe radiation in 10 different bands, with frequencies between 35 to 950 GHz (1 GHz = 109 Hz).

(10 marks)

a) Calculate the wavelengths of the radiation at 35 and 950 GHz.

b) In what parts of the electromagnetic spectrum are these wavelengths

found?

c) Calculate the energy of radiation at these two frequencies in Joules and

in eV.

1eV=1.6x10-19 J

Answer 1

- (a) let v = 35 GHZ as we know and we = c=v7 thus for v=v, = 35 GHz = 35% 107 HZ 950 GHZ = speed of light = 32 108 mis ve frequency of radiation a = wavelength of radiation ELLER 1,= c 3x108 - 35x10? A = 8.57 X163 m for v= V₂ = 950 GHz = 950 x 109 ut - Az = 2 12= 3.168 16hm = 3x108 950x10? These warelengths found in microwave region of elechomgnetic Spectrum.

(6) Energy 494 is given E= hv = hv at v=v, = 35x10" E = he planck's Constant = 6.626 X10-34 JS 6.626x1034 x 35x109 HZ Ei = 2.32 X10-83 Joutes gev = 11.45 x 10"ev? E, 2.38 X10-23 1.6x10-19 e

at V = Vy = 9.50 x10 " HZ E = h v = 6.626x76-34 x 9.5x10" Ez = 6°29 X 10 22 J = 6.29 x lot 1.-22 1.6x1019 ev Ez = 3.93 x 10 Bev