# Acharya Narendra Dev College/Learning Physics through Problem Solving/Quantum Physics

## Problem 1

Calculate the wavelength of the maximum spectral radiancy and identify the region of the electromagnetic spectrum to which it belongs for each of the following:

(a) The 2.7-K cosmic background radiation, a remnant of the primordial fireball.

(b) Human body, assuming a skin temperature of $34^0$ C .

(c) A tungsten lamp filament at 1800 K.

(d) The Sun, at an assumed surface temperature of 5800 K.

(e) An exploding thermo nuclear device, at an assumed fireball temperature of $10^7$ K .

(f) The universe immediately after the Big Bang, at an assumed temperature of $10^38$ K .

We may assume cavity radiation conditions throughout.

## Problem 2

A cavity whose walls are held at 1900 K has a small hole, 1.00 mm in diameter, drilled in its wall. Find the rate at which energy is escaping through this hole from the interior of the cavity.

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