Answer:
Star formation occurs most rapidly in the spiral arms, where the density of interstellar matter is highest.
So we want to know how can we detect infrared rays without an instrument. Infrared rays or heat, are a part of electromagnetic spectrum. We have specialized nerve cells in our skin called thermoreceptors that can detect differences in temperature that are produced by infrared part of EM spectrum.
The extrapolated temperature is used to define the maximum temperature of the mixture relatively than the highest recorded temperature in which the conclusion will effect in a higher specific heat value. Heat is bound to escape from whatever apparatus is using, therefore it is needed to account for the loss of the heat that does not go into increasing the temperature of the mixture.
Explanation:
Given that,
The mean kinetic energy of the emitted electron, 
(a) The relation between the kinetic energy and the De Broglie wavelength is given by :
(b) According to Bragg's law,
n = 1
For nickel, 
As the angle made is very small, so such an electron is not useful in a Davisson-Germer type scattering experiment.
