QQuestion
Prove that with a rectangular glass slab, incident ray and emergent ray are parallel to each other.
WBBSEClass 10Physical ScienceLight – Reflection and Refraction03 Mark2025 Hard
✓Answer
At the first surface O, the ray enters the glass slab from air and is refracted.
According to Snell’s law, ₁μ₂ = sin i / sin r
where,
- i = angle of incidence,
- r = angle of refraction,
- ₁μ₂ = refractive index of glass with respect to air.
At the second surface B, the ray emerges from the glass into air.
Again, by Snell’s law, ₂μ₁ = sin r / sin θ (where θ is the angle of emergence)
Since, ₂μ₁ = 1 / ₁μ₂
⇒ sin i / sin r = sin θ / sin r
⇒ sin i = sin θ
⇒ θ = i
Thus, the angle of emergence is equal to the angle of incidence. Therefore, the emergent ray is parallel to the incident ray. However, it is displaced sideways by a small distance called the lateral shift.
Was this answer helpful?
Related Questions
More WBBSE Hard level questions
1/12
A ray of light is incident normally on one of the faces of a prism of refracting angle A and refractive index μ. If δ = angle of deviation, then establish the relation between μ, A and δ.
In the case of refraction if the angle of incidence is 45° and the refracted ray makes an angle of 60° with the normal, what will be the value of the angle of deviation? If an object of 6 cm in length is placed at a distance of 2.4 cm in front of a convex lens, the image is formed at a distance of 4.8 cm from the lens. What are linear magnification and the length of the image? [1 + 2]
What is Hypermetropia? Which type of lens is used to rectify it? [2+1]
Define dispersion of light. How would you identify monochromatic light and composite light with the help of a prism? [1 + 2]
Write down the relationship between relative refractive index and absolute refractive index. On which factors does the relative refractive index of a medium depend? [1 + 2] OR Show that if a monochromatic light ray passes symmetrically through an equilateral prism then the angle of deviation of that ray will be minimum
What is long-sightedness? What type of lens is used to remedy this defect? [2+1]
Draw refracted rays for the incident rays which are parallel to the principal axis of a convex lens. Mark focus (F). [3] OR Explain the converging action of a convex lens. [3]
A light is incident from air medium on another medium. If the refractive index of this medium is 1.5 and the wavelength of light in this medium is 4000 Å what is the wavelength of light in the air medium ? What is the velocity of the light in this medium? [3] OR As a result of refraction of light through an equilateral prism the angle of deviation becomes 40°. If the path of the ray through the prism is parallel to the base of the prism, determine the angle of incidence at the first surface of prism. [3]
What type of lens is used as a magnifying glass?
Which parameter remains unaltered during refraction of light? (a) Velocity (b) Amplitude (c) Frequency (d) Wavelength
Why is the red colour selected for danger signal lights?
For which value of the angle of incidence in refraction of light is Snell's law not applicable?