When a sphere is heated, then the energy emitted is directly proportional to? (a) Wavelength (b) Frequency (c) Temperature (d) Mass
Exact details depend on the material it is made of, but, for example, if it was made up of iron, if you heat it up enough it glows red hot. It's emitting energy in the form of photons, and these have a frequency that make them appear red.
Heat it up more, and it begins to glow white - it's emitting higher energy photons.
Just exactly this scenario ("black body" radiation) led to the development of the quantum theory, which is such a successful one that our entire global economy depends on it.