Ray Optics And Optical Instruments

Question:

A concave lens with a refractive index of 1.5 is submerged in a medium with a refractive index of 1.65. What kind of lens is it?

Solution:

Concave lenses act like convex lenses if their relative refractive indices are less than 1.

Given,

n₁=1.65, n_g=1.5  

Calculating the relative refractive index is as follows:

1n_g = n_g/n₁ < 1 [As, n₁ > n_g]

Since the lens’s relative refractive index is less than 1, it will act like a convex lens.

Question:

How much power and focus length does a plane glass have?

Solution:

The inverse of optical power, focal length is a measure of how strongly an optical system converges or diverges light. A system with a positive focal length is said to converge light, whereas one with a negative focal length is said to diverge light. So, Power (P) = 1/f.

Since the angle of incidence and emergence with a shift are equal in a plane glass slab, the focal length of a planar surface is infinite. As a result, the rays will collide at infinity, giving them an infinite focal length.

Question:

How does the deviation of light depend on wavelength?

Solution:

The distance between two successive crests or troughs of a wave is known as its wavelength. It is measured in the wave’s direction.

The wavelength has an inverse relationship with the light’s deviation. The light that deviates the greatest has the shortest wavelength.

The letters of the word VIBGYOR are arranged in increasing order of the wavelengths of the many light colors. In other words, Red has the longest wavelength whereas Violet has the shortest.

Question:

Which light does a prism deviated more, blue or red, out of? Give an explanation.

Solution:

The wavelength of light, which is inversely proportional to the equivalent refractive index for that light in medium, determines how light in a medium deviates.

Blue light deviates more in a medium than red light does because blue light’s shorter wavelength results in a higher refractive index, which increases the amount of deviation that is created. Red light’s maximal wavelength corresponds to its lowest refractive index, which results in the least amount of deviation.

Question:

An equilateral prism allows light to travel through it with angles of incidence and emergence that are each equal to 3/5 of the prism’s angle. How much of a divergence is there?

Solution:

Let, Angle of prism = X

Angle of incident i= Angle of emergence e = X

Since prism is equilateral X = 60

So, i = e = 60 x 3/5 = 36

According to prism formula,

Angle of deviation d = i + e – X = 36+36 – 60 = 72 – 60 = 12 degree.

Question:

A reflecting or refracting type of telescope can be used for astronomy. What produces the higher-quality image between the two? Defend your response.

Solution:

Mirror has a strong resolving strength and no chromatic or spherical aberrations.

Question:

What is Refractive Index?

Solution:

Refractive index is the difference between the speed of light in a vacuum and another medium.

The measurement of how much a light ray bends when moving from one medium to another is called the refractive index. It is also known as n = c/v, which is the ratio of the speed of a light beam in a vacuum to that of a light ray in a substance.

Where,

n is the refractive index.

The speed of light in a vacuum is 3 108 m/s, therefore c

In a substance, v represents the speed of light.

Question:

When violet light instead of red light is incident on a lens, how does the focal length of the lens change? Justify your response.

Solution: