In the last years of the nineteenth century, Planck was investigating the problem of black-body radiation first posed by Kirchhoff some forty years earlier. It is well known that hot objects glow, and that hotter objects glow brighter than cooler ones. The electromagnetic field obeys laws of motion similarly to a mass on a spring, and can come to thermal equilibrium with hot atoms. The hot object in equilibrium with light absorbs just as much light as it emits. If the object is black, meaning it absorbs all the light that hits it, then its thermal light emission is maximized. COUNT 14
QSN1 What type of radiation was Planck studying in the late 19th century? ANS1 black-body QSN2 How many years prior to Planck's study had the scientific community first discussed black body radiation? ANS2 forty QSN3 What scientist first studied black body radiation? ANS3 Kirchhoff QSN4 What is required for the electromagnetic field to come to thermal equilibrium? ANS4 hot atoms QSN5 What does a hot object in equilibrium absorb as much as it emits? ANS5 light QSN6 What was Planck studying in the last part of the nineteenth century? ANS6 the problem of black-body radiation QSN7 Who posed the problem of black-body radiation? ANS7 Kirchhoff QSN8 Cooler objects glow less than objects that are what? ANS8 hotter QSN9 What does a black object do to any of the light that hits it? ANS9 it absorbs all the light QSN10 What is maximized as a result of a black object absorbing all the light that hits it? ANS10 thermal light emission QSN11 Planck studied what problem posed originally by Kirchhoff? ANS11 black-body radiation QSN12 If an object is black, what is known about its thermal light emission? ANS12 its thermal light emission is maximized. QSN13 What is known about the light absorption of a hot object in equilibrium with light? ANS13 absorbs just as much light as it emits QSN14 Electromagnetic fields obey what laws? ANS14 laws of motion