Determine the speed of a light ray passing through a glass slab of refractive index 1.5. [c = 3 × 10⁵ m s⁻¹]
WBBSE
Class X
Physical Science
Light – Reflection and Refraction
02 Mark
2026
Refractive index of glass (μ) = 1.5
Speed of light in vacuum (c) = 3 × 10⁵ m s⁻¹
Speed of light in glass (v) = ?
We know, μ = \frac{\text{c}}{\text{v}}
Therefore,
v = \frac{\text{c}}{\text{μ}}
= \frac{3\times10^5}{1.5}
= 2 × 10⁵ m s⁻¹
Hence, the speed of light in the glass slab is 2 × 10⁵ m s⁻¹.
Related Questions
More WBBSE Easy level questions
1/12
Q.
Whether a concave lens is called a converging or diverging lens? Answer with reason.
A.
A concave lens is called a diverging lens. Reason: When parallel rays...
Q.
Write Snell’s law of refraction of light
A.
Snell's law : The ratio of the sine of the angle of...
Q.
What is meant by the principal axis of a concave lens?
A.
The principal axis of a concave lens is an imaginary straight line...
Q.
Determine the angle of deviation for the refraction of light rays from rarer to denser...
A.
The angle of deviation (δ) for light rays passing from a rarer...
Q.
When a ray of light is incident normally on the surface of a glass slab,...
A.
(a) 0° Explanation When a ray of light is incident normally on...
Q.
The least distance of distinct vision for a normal human eye is: (a) 25 cm...
A.
(a) 25 cm Explanation The least distance of distinct vision (near point)...
Q.
Give an example of a natural spectrum.
A.
Rainbow Explanation A rainbow is an example of a natural spectrum. It...
Q.
Write two causes of short-sightedness or myopia. Which type of lens is used to correct...
A.
Myopia may occur due to: Excessive curvature of the eye lens, which...
Q.
For the same angle of incidence, the angles of refraction in three different media A,...
A.
For the same angle of incidence, Angle of refraction in medium A...
Q.
Which color of light undergoes the minimum scattering?
A.
Red light Explanation Red light has the longest wavelength among the colours...
Q.
Explain with a suitable ray diagram the process of formation of image by a concave...
A.
A concave lens always forms a virtual, erect and diminished image of...
Q.
Why is the red colour selected for danger signal lights?
A.
Red colour is selected for danger signal lights because it has the...