Question

Sir. What is the difference between heat and light?

Yours sincerely

Shubhajeet Das

Answer 1

Dear student


Light is a form of energy propagated by electromagnetic waves which is visible to our eyes. Light has several cousins (the same "stuff", but fundamentally differing in frequency) which are not visible, and are classified by human experience and technology.

One of light's cousins is called infrared rays. These we experience as one of the three modes of heat transfer called radiation, because all bodies not hot enough to emit light will emit infrared instead.

Heat is a dynamic energy, which is transfer of energy from a body hot in temperature to a body cold in temperature. Three modes of heat transfer exist: conduction, convection and radiation.

Radiation is via electromagnetic waves, primarily infrared, but for hot enough bodies like the sun, stars, light bulbs, fires, coals, and stove coils, it can also be some visible light.

Conduction is direct heat transfer through elastic collisions among molecules of bodies in contact.

Convection is a mode of heat transfer involving conduction between a solid and a fluid, but the fluid is also able to flow and carry heat with a bulk motion of heat. Should conduction effects not be considered, it is called advection. As a mechanical engineer, though I have been taught advection, I feel there is no purpose for even knowing that word. All convection must exist with conduction as well.


Hope you understand the difference.