Optics Summary PDF

This summary is to be split into 5 separate sections under the following large headings Light Basics Light is a form of energy that travels away from the source producing it at a speed of about 3 x 108 ms-1. Light undergoes the 5 wave phenomena meaning it has wave-like nature. Light usually travels...

This summary is to be split into 5 separate sections under the following large headings Light Basics Light is a form of energy that travels away from the source producing it at a speed of about 3 x 108 ms-1. Light undergoes the 5 wave phenomena meaning it has wave-like nature. Light usually travels in straight lines. Reflection Definition: The bouncing of light off an object is called reflection. Definition: The Refractive Index of a Medium is the ratio of the sine of the angle of incidence to the sine of the angle of refraction when light travels from a vacuum into that medium. Diffuse Reflection is the reflection of light off a rough surface in which it is scattered in all directions. Regular Reflection is the way in which light reflects off smooth surfaces like mirrors. A real image is formed due to the actual intersection of light rays. A virtual image is formed by the apparent intersection of light rays. LAWS OF REFLECTION OF LIGHT Law 1: The incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane. Law 2: The angle of incidence is equal to the angle of reflection (i = r) Spherical Mirrors Concave mirrors produce Real and Virtual images. Convex mirrors produce only Virtual images. FOR A CONVEX MIRROR: The image is always virtual and located behind the mirror. The image is always diminished. The nearer the object is to the mirror the bigger the image. FOR A CONCAVE MIRROR: If the object is outside the focus the image is real and located in front of the mirror. If the object is inside or at the focus the image is virtual and is located behind the mirror. 1 1 1 𝑓 1 𝑢 𝑣 The formula = + is used calculate focal length (f) object distance (u) and image 1 distance (v). is a minus for a convex mirror and is minus for a virtual image. 𝑓 𝑣 Concave mirror used by dentists and in floodlights. Convex mirrors used in supermarkets and cars to provide a wide field of view. Refraction Definition: The bending of a ray of light when it goes from one medium to another is called refraction. Laws of Refraction Law 1: The incidence ray, normal and the refracted ray are all in the same plane. Law 2: The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for two given media. The 2nd law is called Snell’s Law. Light going from denser to rarer median → refracted towards normal. Light going from rarer to denser median → refracted away from normal. Critical angle: is the angle of incidence whose corresponding angle of refraction is 90 degrees. OPTICAL FIBRE A very thin transparent rod (usually of glass) through which light can travel by total internal reflection is called an optical fibre. Refractive index (n) = real depth velocity in medium 1 = apparent depth velocity in medium 2 = 1 sin 𝐶 = 𝐬𝐢𝐧𝒊 𝐬𝐢𝐧𝒓 Lenses There are two types of lenses, concave and convex. Concave lenses (diverging) produce Virtual images. Convex lenses (converging) produce Real and Virtual images. The formula = + is used calculate focal length (f) object distance (u) and image 1 1 1 𝑓 1 𝑢 𝑣 1 distance (v). is a minus for a diverging lens and is minus for a virtual image. 𝑓 𝑣 1.𝑃 𝑓 Power of a lens is = The human eye uses a lens which alongside cornea produces a converging system. = 𝑃1 + 𝑃2 , P1 and P2 = powers of the two lenses in contact.