Optical Instruments - Projector



  1. Bulb with high brightness is used.
  2. The bulb must be placed at the centre of curvature of the concave mirror.
Concave mirror
  1. The function of the concave mirror is to reflect and focus light that shines on it to the direction of the condenser.
  2. This is to increase the brightness of the image.
  1. The condenser consists of two Plano-convex lenses.
  2. The function of the condenser is to focus all the light that brightens the whole slide.
  3. It also acts as a heat insulator to stop heat from the bulb so it does not spoil the slide.
  1. The slide acts as the object.
  2. It is located at a distance between f and 2f from the projector lens so that the image produced is real and magnified.
  3. It is purposely placed upside down so that the image forms on the screen looks upright.
Projector Lens
  1. The projector lens projects the image on the screen that is placed a few meters away.
  2. It can be adjusted to focus a sharp image.
Image The image produced is
  1. real (it form on a screen)
  2. magnified
  3. inverted (Since the slide is placed upside down, hence the image looks upright)