A person can see distant objects distinctly but is unable to see nearby objects in a perfect way. Predict the probable cause and suggest the corrective measure for such problem.

The person is suffering with hypermetropia. In this problem the eyeball is too short or the power of the lens is very less. Hence, the image is formed behind the retina. So it causes blurred vision. This defect of vision can be corrected with the use of convex lens of suitable focal length. This helps in converging the rays and, they meet on the retina to form the image.

Write the names of the different refractive medium of eyeball in proper sequence.

Cornea and lens are two media through which light is refracted as it enters into the eye. Most of the refraction for the light rays occurs at the outer surface of the cornea. The crystalline lens of the eye provides the finer adjustment of focal length required to focus objects at different distances on the retina.

To rectify which defects in the eye's vision, spectacles of convex lens and concave lens are used?

Convex lens is used for the correction of the defect of eye called hypermetropia. The image of the object is formed behind the retina and hence, it appears blurred. This defect is also known as far-sightedness. Myopia or short-sightedness is corrected by concave lens. Concave lens is a diverging lens. It helps to form the image on the retina that if formed in front of the retina due to myopia.

Mention one function of lens of eyeball.

The lens of eyeball forms the image of objects on the retina of the eye. The objects are at different distances from the lens of the eyeball and the distance of the retina and the eyeball is almost fixed. The focal length of the lens of the eyeball is so adjusted by the muscles that image is always formed on the retina.

What is a diverging lens?

A lens that diverges or spread out the light rays falling on it is called a diverging lens. The perpendicular distance between the light rays increases after refraction. Concave lens is a diverging lens. After refraction through concave lens, the rays of light do not actually meet hence, the real image is never formed by this lens.

What will be the velocity and wavelength of light in a medium of refractive index 1 . 5 if the wavelength of the light is 6000 A ∘ in air medium?. Take the speed of light in air = 3 × 10 8 m s - 1 .

The refractive index of a medium is defined as the ratio of speed of light in air to the speed of light in that medium. Hence, the speed of light in the given medium: v = c μ = 3 × 10 8 1 . 5 = 2 × 10 8 m s - 1 The frequency of a wave does not change as it enters into another medium. Hence, the wavelength of light in the given medium: λ n e w = v c × λ = 2 × 10 8 ms - 1 3 × 10 8 ms - 1 × 6000 A ∘ = 4000 A ∘ Velocity of light will be 2 × 10 8 m s - 1 and the wavelength of light will be 4000 A ∘ .

The principal section of a prism is an equilateral triangle. If a ray of light is incident at an angle of 30 ∘ on one of the refracting surfaces and emerges at an angle of 45 ∘ from the other refracting surface, what is the angle of deviation?

Given: For a prism of a cross-section of an equilateral triangle, the angle of prism, A = 60 ∘ The angle of incidence, i = 30 ∘ The angle of emergence, e = 45 ∘ The formula for total deviation by a prism: δ = i + e - A ⇒ δ = 30 ∘ + 45 ∘ - 60 ∘ = 15 ∘ The angle of deviation will be 15 ∘ .

What is dispersion of light? Will there be dispersion of white light within a glass slab after refraction when white light is incident on the glass slab at an angle of 45 ∘ ?

Splitting of white light into its constituent colours is called dispersion of light. The phenomenon is observed when white light passes through a prism. The light of diffrerent wavelength(colours) travel with different speed in a medium other than air(vacuum), hence all colours travel through separate paths. When white light falls obliquely on a rectangular glass slab, dispersion is not observed. The slab has two parallel refracting surfaces. The light passes from air to glass at the first interface and again it passes from glass to air on the second interface. Hence, the deviation produced on one surface is cancelled as it crosses the another surface.

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 5 - Light>West Bengal Board-2019>Q 14

MEDIUM

10th West Bengal Board

IMPORTANT

Earn 100

How many rectangular surfaces are there in a prism?

Important Questions on Light

MEDIUM

10th West Bengal Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 5 - Light>West Bengal Board-2019>Q 15

What is refractive index of a medium?

MEDIUM

10th West Bengal Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 5 - Light>West Bengal Board-2019>Q 16

Which type of defect of vision is rectified by a convex lens?

MEDIUM

10th West Bengal Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 5 - Light>West Bengal Board-2019>Q 17

What type of mirror is used by dentists? Why does a ray of light not deviate as a result of refraction through a glass slab?

MEDIUM

10th West Bengal Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 5 - Light>West Bengal Board-2019>Q 18

When an object is placed $20 cm$ away from a convex lens, no image is obtained on either side of the lens. What is the focal length of the lens? If the refractive index of glass with respect to air is $1.5$ , what is the refractive index of air with respect to glass?

HARD

10th West Bengal Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 5 - Light>West Bengal Board-2019>Q 19

The length of an object is $5 cm$ . An image of length $10 cm$ is obtained when it is placed at a distance of $2 cm$ in front of a convex lens. What are linear magnification and image distance?

MEDIUM

10th West Bengal Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 5 - Light>West Bengal Board-2019>Q 20

Mention one use of each of ultraviolet rays and gamma-ray.

MEDIUM

10th West Bengal Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 5 - Light>West Bengal Board-2020>Q 21

If a beam of red light and a beam of violet light are incident at the same angle on the inclined surface of a prism from air medium and produce angles of refraction $r and v$ respectively. Which of the following is correct?

EASY

10th West Bengal Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR SCIENCE>Chapter 5 - Light>West Bengal Board-2020>Q 23

What is meant by the pole of a spherical mirror?