CBSE Class 10 Practicals Science Chapter 10 Refraction of light for Topic To Study Laws of Refraction through Glass Plate. Students get here clear concept at this page.
How to find find Laws of Refraction through Glass Plate | CBSE Class 10 Practicals | Refraction of light Practicals | Class 10 Science Practicals | Class 10 Projects | Refraction of light Chapter Projects
To Study Laws of Refraction through Glass Plate
Dear students we know that when a ray of light passes from one transparent medium to another transparent medium it changes the direction, this phenomena is known as refraction of light. During refraction, rays of light obey certain conditions, termed as laws of refraction. So let’s learn the laws of refraction through this experiment.
Objective of the experiment….
To study the laws of refraction using a glass slab.
Instruments required for the experiment…..
Wooden board, plain paper and pin, thin glass plate, glass slab, laser light (green or red colour), pencil, scale, protractor, small wax blot etc.
Theory used for the experiment…..
We are going to illustrate the laws on the basis of following assumptions.
- When a ray of light passes through any transparent material to another transparent material it changes direction and velocity, this is called as refraction of light.
- Depending upon the optical density of transparent material, the angles in corresponding media are different.
- In refraction of light, angle of incident and angle of refractions are not congruent like reflection. But here they are in proportion with each other.
Formula used…..
n = sini/sinr
Where,
- n =Refractive index
- i = angle of incidance
- r = angle of refraction.
Diagram showing the experimental condition….
Procedure to find the focal length….
- Take a plain paper and fix it on the wooden board with the help of pins.
- Take two wax blot, place on wooden board and fix a glass plate in it such that the glass plate appear to be hold on table exactly perpendicular to surface of board.
- Place the protractor at the middle of plane of glass plate and mark a point at 900 and draw a line, label it as normal. Do the same step for either side of plate.
- Now hold the laser light at some distance from the plate, switch on it and allow beam of light falls on the plate at angle of 300 with the normal. Mark this as angle of incidence. Fix two pins on the wooden board along the path of this beam of light and mark them ray PQ i.e. incidence ray.
- Observe the path of this ray on either side of plate. Take two more pins and fix them on board and label it as refracted ray RS. Mark the angle between the refracted ray and normal, i.e. angle of refraction.
- Now stop the beam of light and using scale and pencil, trace the incident ray, refracted ray. Measure the corresponding angle of incidence and angle of refraction and note down in observation table.
- Repeat the same procedure by taking different values of angle of incidence and complete the table.
Observation table…
Sr No. | Angle of incidence (i) | Angle of refraction (r) | Ratio of sini/sinr |
1 | 300 | ||
2 | 450 | ||
3 | 600 |
Result / Conclusions:
- The incident ray and refracted ray are appears on opposite sides of normal.
- The incident ray, refracted ray and normal lies in same plane at the point of incidence.
- Angle of incidence is in proportional with the angle of refraction. i.e. ratio of sine of angle of incidence to sine of angle of refraction is constant. This constant is called as refractive index of material.
Precautions that should be followed while performing experiment….
- The position of glass plate should be exactly perpendicular to surface of board.
- Pins should be fixed exactly on the path of laser beam.
- All the angles should be measured accurately.
Some important questions that needs to revised for the experiment…
Q.1) State the laws of refraction.
Answer:
- Incident ray, refracted ray and normal lies in same plane at the point of incidence, and incident ray and refracted rays lies on opposite side of normal.
- For given pair of media, the ratio of sine of angle of incidence to the sine of angle of refraction is constant.
n= sini/sinr
Where, =Refractive index of material
Q.2) State the applications of refraction of light in our daily routine.
Answer:
Twinkling of stars, advanced sunrise, delayed sunset are some common examples of refraction of light.
Q.3) Explain the path followed by rays of light when travels from different media.
Answer:
- When a ray of light passes through optically rarer medium to optically denser medium, refracted ray bends towards the nor.al. Here angle of incidence is greater than angle of refraction.
- When a ray of light passes through optically denser medium to optically rarer medium, refracted ray bends away from the normal. Here angle of incidence is less than angle of refraction.