To Verify the Laws of Refraction (Glass Slab) (Class 10 Physics Practical)
To verify Snell's Law by measuring incident and refracted angles when light passes through a glass slab.
TL;DR: To verify Snell's Law by measuring incident and refracted angles when light passes through a glass slab.
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Aim: To verify Snell's Law by measuring incident and refracted angles when light passes through a glass slab.
Materials Required
- Glass slab
- Pins (4-5)
- Protractor
- Meter scale
- Paper
- Pencil
- Wooden board
- Source of light
Theory
Refraction is the bending of light when it passes from one medium to another. Snell's Law states: n1 sin(i) = n2 sin(r), where n1 and n2 are refractive indices and i and r are angles of incidence and refraction respectively. The incident ray, refracted ray, and normal lie in the same plane.
Procedure
- Place the glass slab on a paper and draw lines along its outline
- Draw a normal to the glass slab at the point of incidence
- Draw an incident ray at a specific angle to the normal
- Place pins along the incident ray and mark the point where it strikes the glass surface
- View the refracted ray from the other side and place pins along it
- Mark the path of the refracted ray on the paper
- Remove the slab and measure the angle of incidence and angle of refraction
- Calculate sin(i) and sin(r) for each observation
- Repeat with different angles and note that sin(i)/sin(r) remains approximately constant
Observation
When light enters the glass slab, it bends towards the normal (angle of refraction is less than angle of incidence). When light emerges from the glass slab, it bends away from the normal, becoming parallel to the original incident ray. The ratio sin(i)/sin(r) is constant for glass (refractive index ≈ 1.5).
Result
Snell's Law is verified. The ratio sin(i)/sin(r) equals approximately [value], confirming the constant relationship between angles and refractive indices.
Precautions
- Place the glass slab firmly on the paper to prevent movement
- Draw the normal at right angles to the glass surface accurately
- Measure angles from the normal, not from the surface
- Use sharp pins and observe from directly above
- Take readings at different angles to verify consistency
Viva Questions
What is Snell's Law?
Snell's Law states that n1 sin(i) = n2 sin(r), relating the angles and refractive indices of two media.
Why does light bend when passing from one medium to another?
Light travels at different speeds in different media. The change in speed causes the change in direction, resulting in refraction.
What happens when light emerges from the glass slab?
When light emerges from the glass slab, it bends away from the normal and becomes parallel to the original incident ray.
What is the refractive index of glass?
The refractive index of glass is approximately 1.5, meaning light travels 1.5 times slower in glass than in vacuum.
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