Cosmologists have deduced that soon after the Universe was formed it was filled with electromagnetic radiation in the form of intense gamma-rays. They have also deduced that the Universe has been expanding since that time. One effect of this expansion is that the electromagnetic radiation that fills the Universe is now in the microwave region of the spectrum. Here are three statements about the effects of the Universe expanding on the electromagnetic radiation that filled the early Universe: 1 The expansion has caused an increase in the frequency of the radiation. 2 The expansion has caused a decrease in the wavelength of the radiation. 3 The expansion has caused frequency to change in direct proportion to wavelength. Which of the statements is/are correct?

Answer:

19) A

When the universe was formed, it was filled with electromagnetic radiation in the form of intense gamma-rays. Now it is in the microwave region of the spectrum.

If you remember the electromagnetic spectrum, you will know that frequency decreases as we shift from gamma to microwave and wavelength increases. So, statements 1 and 2 are wrong.

Also, frequency is indirectly proportional to wavelength. So, statement 3 is also wrong.