Light Flashcards
Specular Reflection
when light hits a smooth and shiny surface(glass) it is reflected at the same angle
Diffuse Reflection
Diffuse reflection is when light hits an object and reflects in lots of different directions. This happens when the surface is rough.
Laws of Reflection
When light wave hits a flat surface, the angle of incidence is the same as the angle of reflection
The incident ray, the reflected ray and the normal, all lie in the same plane
During reflection, while the wave direction changes, the wave speed, wavelength and frequency remain the same
Features of virtual Images formed by a plane mirror
The image is the same size as the object.
The image is as far behind the mirror as the object is in front of the mirror.
The image is upright - the same way up as the object.
The image is virtual because the image appears to be behind the mirror.
The image is laterally inverted, the ‘left’ of the object now appears on the ‘right’ side and the ‘right’ of the object appears to be the ‘left’ side of the image - lateral inversion.
Real and Virtual Images
A real image can be displayed on a screen or piece of paper or on a wall. A virtual image can be seen with the eyes but it’s impossible to display the image on a screen. A real image is always inverted whereas a virtual image is always upright.
Refraction
Refraction is due to change of speed of light in different medium. The change in speed of light ray in different medium results in change in direction of propagation of light.
It happens whenever the waves are incident to the surface at an angle different to the normal to the surface
Laws of Refraction of light
Light travelling from less dense medium (Eg. Air) to denser medium (Eg. Water), bends towards normal.
Light travelling from denser medium (Eg. Water) to less dense medium (Eg. Air), bends away from normal.
If the light ray enters another medium perpendicularly to the boundary, there is no deviation of the ray even when there is change in speed of light.
Polychromatic Light in Prisms
Light travelling from less dense medium (Eg. Air) to denser medium (Eg. Water), bends towards normal.
Light travelling from denser medium (Eg. Water) to less dense medium (Eg. Air), bends away from normal.
If the light ray enters another medium perpendicularly to the boundary, there is no deviation of the ray even when there is change in speed of light.
Refractive Index
Refractive index is the extent to which light is refracted when it enters a medium.
Refractive index of a medium can be defined as the ratio of the speed of refracted light in vacuum to its speed in the medium.
𝑹𝒆𝒇𝒓𝒂𝒄𝒕𝒊𝒗𝒆 𝑰𝒏𝒅𝒆𝒙 𝒐𝒇 𝒂 𝒎𝒆𝒅𝒊𝒖𝒎 (𝒏)= 𝑺𝒑𝒆𝒆𝒅 𝒐𝒇 𝒍𝒊𝒈𝒉𝒕 𝒊𝒏 𝒗𝒂𝒄𝒖𝒖𝒎(𝒄) / 𝑺𝒑𝒆𝒆𝒅 𝒐𝒇 𝒍𝒊𝒈𝒉𝒕 𝒊𝒏 𝒎𝒆𝒅𝒊𝒖𝒎 (𝒗)
𝑹𝒆𝒇𝒓𝒂𝒄𝒕𝒊𝒗𝒆 𝑰𝒏𝒅𝒆𝒙 𝒐𝒇 𝒂 𝒎𝒆𝒅𝒊𝒖𝒎 (𝒏)= 𝐬𝐢𝐧 𝒊 / 𝐬𝐢𝐧 𝒓
𝑹𝒆𝒇𝒓𝒂𝒄𝒕𝒊𝒗𝒆 𝑰𝒏𝒅𝒆𝒙 𝒐𝒇 𝒂 𝒎𝒆𝒅𝒊𝒖𝒎 (𝒏)= 𝟏 / 𝒔𝒊𝒏 𝒄
Wavelength remains constant before and after diffraction
