Light & Lens Explorer
Switch between reflection, refraction, total internal reflection, and converging-lens modes to reason directly from ray diagrams.
Learning goals
- Use the normal, angle of incidence and angle of reflection
- Apply the law of reflection in constructions, measurements and calculations
- Use the normal, angle of incidence and angle of refraction
- Apply sin i divided by sin r as a constant for a fixed pair of media
- Define refractive index as vacuum light speed divided by medium light speed
Learning objectives
- Use the normal, angle of incidence and angle of reflection
- Apply the law of reflection in constructions, measurements and calculations
- Use the normal, angle of incidence and angle of refraction
- Apply sin i divided by sin r as a constant for a fixed pair of media
- Define refractive index as vacuum light speed divided by medium light speed
- Explain the critical angle
- Explain the conditions for total internal reflection
- Describe how a thin converging lens acts on a light beam
- Define the focal length of a converging lens
- Construct real and virtual image ray diagrams for a thin converging lens
- Describe lens images as real or virtual, magnified or diminished, and upright or inverted
A converging lens of focal length 10 centimetres with an object 25 centimetres away. The image is real, inverted, diminished, 16.7 centimetres from the lens.
- Object distance, u
- 25.0 cm
- Image distance, v
- 16.7 cm
- Magnification
- 0.667
- Image
- Real, inverted, diminished
- Angle of incidence, i
- 35.0 °
- Angle of reflection
- 35.0 °
- Angle of refraction, r
- 22.5 °
- sin i / sin r
- 1.500
- Critical angle, c
- — °
Try this
0 of 4 doneMake a real image the same size as the object. (not done yet)
The object is at 2F, so the image is at 2F on the other side: real, inverted and the same size.
Make a virtual image three times the height of the object. (not done yet)
With the object nearer than F the rays leave diverging. Traced back, they meet at a virtual, upright, magnified image on the object's side, as in a magnifying glass.
From glass into air, find the angle of incidence where the refracted ray skims the surface. (not done yet)
That is the critical angle: sin c = 1/n, so c ≈ 42° for glass. Entering a medium with a smaller refractive index, light bends away from the normal.
Make total internal reflection happen. (not done yet)
It needs light in the denser medium hitting the boundary at more than the critical angle. Optical fibres trap light this way.