Physics · Science General

Optics and Light Properties

2,019 Questions

Optics and light properties focus on the behavior of light, including reflection, refraction, dispersion, and polarization. This topic also covers the wave nature of light, illumination, and the functioning of optical instruments like microscopes. Questions on these concepts are common in general science sections of SSC, Railways, and State exams.

Reflection and mirrorsRefraction and mediumsLight wave theoriesPolarization and intensity

Optics and Light Properties Questions

Multiple choice physics oscillations and waves huygen's wave theory refraction of water waves reflection and refraction at plane surfaces theories on light

When the beam of light travels in a medium with lesser velocity than that of in vaccum then the value of wavelength and frequency will respectively

  1. Increase, decrease

  2. Increase, unchanged

  3. Decrease, unchanged

  4. Decrease, decrease
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Energy $=\dfrac{4c}{\lambda }=4\nu $     which is constant.
Here, velocity is decreasing so, to make constant energy $\lambda$ should also decrease and frequency remains constant.

Multiple choice physics oscillations and waves huygen's wave theory refraction of water waves reflection and refraction at plane surfaces theories on light

Consider a light wave that passes from air into a very thick clear glass block that has its opposite internal side mirrored (facing into the glass). The light ray passes into the glass block at an angle greater than $0^{\circ}$ and less than $90^{\circ}$, strikes the mirrored surface and reflects back through the glass into the air.
What happens while the light ray is in the glass block but before it strikes the mirrored surface?

  1. The frequency of the waves increases

  2. The frequency of the waves decreases

  3. The wavelength of the waves decreases

  4. The velocity of the waves decreases

  5. The period of the waves increases
Reveal answer Fill a bubble to check yourself
C,D Correct answer
Explanation

When a light ray enters in a medium of higher refractive index from a lower one, the speed of the wave decreases as $v=\dfrac{c}{\mu}$

Since $\lambda=\dfrac{v}{\nu}$ and the frequency remains unchanged,
$\lambda=\dfrac{\lambda _0}{\mu}$
Hence the wavelength and the velocity of the waves decreases.

Multiple choice physics oscillations and waves huygen's wave theory refraction of water waves reflection and refraction at plane surfaces theories on light

Assertion (A) : Velocity of light is more in rarer medium than in denser medium
Reason (R) : Light waves are longitudinal mechanical waves

  1. Statement A is correct R is wrong

  2. Statement A is correct R is right

  3. Statement A and R both are correct but R is not explaining A

  4. Statement A and R both are correct and R is explaining A
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Velocity of light is more in rarer medium than in denser medium because speed of light in a medium is given by $\dfrac{c}{\mu }$ where, c is speed of light in vacuum and $\mu $ is refractive index of medium. Since denser medium has more $\mu $ than rarer medium, the speed of light is less in medium. Light waves are transverse electromagnetic waves.

Multiple choice physics oscillations and waves huygen's wave theory refraction of water waves reflection and refraction at plane surfaces theories on light


(A) Light is a form of electromagnetic radiation and non-mechanical waves.
(B) Light waves do not require a material as a medium for propagation.

  1. Only A is true.

  2. Only B is true.

  3. Both A and B are true.

  4. Both A and B are false.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Both A and B are true,
Light is a form of electromagnetic radiation and a non-mechanical wave. It does not require a material as a medium for propagation. Hence, it can travel through space.

Multiple choice physics oscillations and waves huygen's wave theory refraction of water waves reflection and refraction at plane surfaces theories on light

When a ray of light is refracted, the wavelength of the refracted light changes. Identify which of the following explain this phenomenon?
I. Some of the energy of the incident ray is carried away by the reflected ray
II. The boundary surface absorbs some of the energy of the incident ray
III. The incident and refracted rays do not travel with the same velocity

  1. I only

  2. II only

  3. III only

  4. I and II only

  5. I, II, and III
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Wavelength of the light in a medium $\lambda _m = \dfrac{v _m}{\nu}$ where $v _m$ is the velocity of light in that medium
The velocity with which the incident and the refracted ray travels is not same but the frequency of both the rays is same. Hence the wavelength of the refracted light changes w.r.t the incident light.
Hence option C is correct.
Multiple choice physics oscillations and waves huygen's wave theory refraction of water waves reflection and refraction at plane surfaces theories on light

Calculate the wavelength of light when it passing through diamond whose refractive index is 2.4 given that wavelength of light in air is 500 nm.

  1. 208 nm

  2. 357 nm

  3. 500 nm

  4. 700 nm

  5. 1,200 nm
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given :   $n = 2.4$              $\lambda _a = 500$ nm

$\therefore$ Wavelength of light in diamond        $\lambda _d = \dfrac{\lambda _a}{n}  =\dfrac{500}{2.4} =208$  nm

Multiple choice physics oscillations and waves huygen's wave theory refraction of water waves reflection and refraction at plane surfaces theories on light

Ray optics holds good when characteristic dimensions are

  1. Of the same order as the wavelength of light

  2. Much smaller than the wavelength of light

  3. Of the order of one millimetre

  4. Much larger than the wavelength of light
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Ray optics holds good when characteristic dimensions are much larger than the wavelength of light.

Multiple choice physics light, shadows and images introduction to reflection of light light and sight images in plane mirror

For a total internal reflection, which of the following is correct?

  1. Light travel from rarer to denser medium.

  2. Light travel from denser to rarer medium.

  3. Light travels in air only.

  4. Light travels in water only.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The total internal reflection occurs when the ray of light is reflected totally into the same medium even without the presence of a mirror. The total internal reflection occurs when a ray of light travels from denser medium to rarer medium.

Multiple choice physics light, shadows and images introduction to reflection of light light and sight images in plane mirror

Which of the following statement is/ are correct?
I. A person suffering from myopia can see distant obhects clearly.
II.. The bluish color of water in deep sea is only due to reflection of sky in water.
III. In vacuum, all the colored of the light move with the same speed.
IV. At noon, the sun appears white as light is least scattered

  1. I only

  2. II only

  3. I and II only

  4. III and IV only
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Myopia is the inability to see objects clearly when they're too far away. People with myopia can often read or see items within a few feet of their face, but distant objects appear blurred. This condition usually develops in an eyeball that's too long from front to back.

The ocean looks blue because red, orange and yellow (long wavelength light) are absorbed more strongly by water than is blue (short wavelength light). So when white light from the sun enters the ocean, it is mostly the blue that gets returned.

Multiple choice physics light, shadows and images introduction to reflection of light light and sight images in plane mirror

The phenomenon that leads to the bouncing back of light rays is called-

  1. Diffraction

  2. Reflection

  3. Dispersion

  4. Refraction
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
$ \bf{Diffraction} $ is the phenomenon of bending of light waves around the corners of an obstacle or aperture, placed in the path of light beam. 

$ \bf{Reflection} $ is the phenomenon in which light rays on striking a polished surface(such as a mirror) bounce back or are sent back into the same medium. 

$\bf{Dispersion} $ is the phenomenon of splitting of white light into its component colours (VIBGYOR) on passing through a glass prism.

$ \bf{Refraction} $ of light is the phenomenon of bending of light or change in the direction of light, when it passes obliquely from one transparent medium to another.

Hence, the correct answer is OPTION B. 
Multiple choice physics light, shadows and images introduction to reflection of light light and sight images in plane mirror

The phenomenon in which light that strikes a surface is thrown back into the same medium is called -

  1. reflection

  2. reflex action

  3. refraction

  4. regression
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
$ \bf{Reflection} $ is the phenomenon in which light rays on striking a polished surface(such as a mirror) bounce back or are sent back into the same medium. 

A $\bf{Reflex\ action} $ is an involuntary and nearly instantaneous movement in response to a stimulus.
 

$ \bf{Refraction} $ of light is the phenomenon of bending of light or change in the direction of light, when it passes obliquely from one transparent medium to another.

$ \bf{Regression} $ is a technique for determining the statistical relationship between two or more variables where a change in a dependent variable depends on the change in one or more independent variables.

Hence, the correct answer is OPTION A.