2physic

• *Definition of light and visible light -Light is defined as the electromagnetic radiation with wavelengths between 380 and 750 nm which is visible to the human eye. -Visible light – portion of the electromagnetic spectrum that is visible to the human eye wavelength range (λ): 380 − 750 nm
• *Law of reflection The angle of reflection θr is always equal to the angle of incidence θi with respect to the normal. equation= θi=θr , θi- incidence θr- reflection • the ray of light is traveling in a straight path • the reflection is always inverted
• *Refraction - governed by snell’s law Equation : n1 sin θ1 = n2 sin θ2 h1- index of refraction of material 1 n2- index of refraction of material 2 θi- angle in material 1 θr- angle oin material 2 Index of refraction (n) equation : n=c/v c-speed of light in vacuum 8 c=3x10 m/s v- speed of light in the medium
• *Index of refraction (n) vs speed of light equation : n1 v1 = n2 v2 If index of refraction is large, the speed of light in that medium is small If index of refraction is small, the speed of light in that medium is large
• *Definition of total internal reflection Complete reflection of a ray of light within a medium back into the medium. In other words, the incident light or any of its portions is not refracted. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle.
• *Definition of polarization Polarized waves are light waves in which the vibrations only occur in a single plane. Polarized light is consisting of waves in which the direction of vibration is the same for all waves. In the image in the right, you can see that a plane polarizer polarized light to vibrate on only one plane.
• *Difference between mirror and lenses -Mirror a polished or smooth surface (as of glass) that forms images by reflection

  -Lens is a transparent device with two curved surfaces, usually made of glass or plastic, that uses refraction to form an image of an object
• Real image


  One that is formed when rays of light are directed/converged in a fixed point. A real image can be projected or seen on a screen.
• Real images


  • Images on a cinema screen
  • Image formed in our retina
  • Image in camera film
• Virtual image


  Any image that cannot be obtained on a screen. The rays of light that form a virtual image never converge therefore a virtual image can never be projected onto a screen.
• Virtual image


  • Your reflection in the mirror
• Real images


  • Produced by intersecting/converging rays
• Virtual images


  • Produced by diverging rays
• Real images


  • Can be projected on a screen
• Virtual images


  • Cannot be projected on a screen
• Virtual images


  • Always upright
• Real images


  • Always inverted
• *Difference between concave and convex mirrors 1. Concave Mirror (Convergent mirror) positive focal length (+)

  • curved inwards towards the centre

  • It is also known as a converging mirror because

  it brings incoming parallel rays together. It

  causes these rays to converge.

  • Can produce real and virtual images
• *Definition of focal length -focal length half of radius :f r/2 -¼ of diameter :f d/4 focal length can be calculated using by radius of a diameter depending on the given
• *Difference between Converging lens and Diverging lens Converging lens () + Diverging lens )( -
• Convex Mirror (Divergent Mirror) negative focal length(-) • curved outwards against the centre • It is also known as a diverging mirror because it causes rays to diverge upon reflection. • Can only produce virtual images
• The mirror is the apparatus which reflects the light falling on them. Lenses are the ones that manipulate the light. Both forms an image.