Question

Which of the following properties of laser beam can be used to measure long distances?
A. It is very intense
B. It is highly monochromatic
C. It is an unidirectional beam of light
D. All of these

Answer 1

Hint: Before attempting this question, one should have prior knowledge about the properties of laser beam and also remember that laser beam which is generated by the intensively focusing narrow light which is amplified, use this information to approach the solution of the question.

Complete answer:
A laser is a device which uses stimulated radiation to project a highly focused narrow beam of light which is amplified. Lasers have three properties: coherence, monochromatic properties and collimation.
In other words, Lasers are beams of light that are focused on one spot. If an electron is excited from lower to higher states of energy, it would inevitably want to fall back to its lower state of energy.

It will emit a photon while doing this. This phase is called stimulated emission. Stimulated emission is the mechanism of interacting with an excited atomic electron by an incoming photon. This interaction releases a fresh photon with the same energy with the same p.

However, this form is surpassed by absorption, in which an absorbed photon's energy induces a similar, yet opposite, atomic transition. The rate of stimulated emission exceeds that of absorption and optical amplification is possible when population inversion is present, meaning there are more electrons in excited states than in lower energy states. This is the precondition for laser lightening. This is what gives the property of coherence to lasers and the capacity to emit light continuously. A laser allows several atoms to emit trillions of photons at once, so that they can line up to form a focused beam of light. When a photon enters an already excited atom, two photons of light are provided out by the excited atom. This is called stimulated photon amplifying emission. These are some properties of laser and the last property of laser is collimation which means the light from a laser is emitted as a directed thin beam at one spot.

This happens because there are two almost opposite mirrors on the front and back of the laser cavity from which the atoms bounce back and forth. The back mirror is mirrored almost perfectly, while the front mirror reflects about 99 percent, letting out 1 percent of the beam. This percentage of 1 is the beam we see. While the light bounces back and forth between the mirrors, because of stimulated emission, it becomes intensified.

So, the correct answer is “Option D”.

Note:
In the above solution we used the term “light” which can be explained as electromagnetic radiation which can be detected with the human eyes where the visual light has wavelength between 380 to 750m. The properties of light such as reflection in which light gets bounced off the material.