Refraction, total internal reflection and lenses

Integrated ScienceLight & SoundAges 14–15

Top half: a light ray travels from medium n₁ into medium n₂ — drag the light source to change the angle of incidence and watch the angle of refraction follow Snell's law n₁·sin i = n₂·sin r, including total internal reflection once the angle exceeds the critical angle. Bottom half: an object sits in front of a converging or diverging lens — drag the object to change the distance d, and three principal rays construct the image while the formula 1/f = 1/d + 1/d′ gives its position, nature and magnification.