Light

• How are real images formed?


  Real images are formed when rays converge and can be captured on a screen.
• What distinguishes virtual images from real images?

  Virtual images are formed when rays diverge and cannot be captured on a screen.
• What are luminous objects?


  Luminous objects emit light on their own in all directions.
• How do we see non-luminous objects?

  Non-luminous objects can only be seen in the presence of a light source, as light is reflected off their surfaces into our eyes.
• What happens to white light when it shines on a blue surface?

  Blue light is reflected, making the object appear blue.
• Why does a black surface appear black?

  A black surface absorbs all colors of light and reflects none.
• What is reflection in terms of light?

  Reflection is the bouncing of light off a mirror.
• What are the characteristics of images formed by plane mirrors?

  • Virtual
  • Upright
  • Same size and distance from the mirror
  • Laterally inverted
• What are some uses of mirrors?

  • Periscopes
  • Vision tests in small rooms
  • Security mirrors (convex)
  • Blind corner mirrors (wider field of vision)
  • Dentists to produce enlarged images of teeth
• What is the difference between concave and convex mirrors?

  Concave mirrors:

  • Inner side of spherical mirror reflecting
  • Form inverted and real images
  • Size depends on the position of the object

  
  

  Convex mirrors:

  • Outer side of spherical mirror reflecting
  • Form virtual and erect images
  • Image is always smaller than the object
• What are the types of reflection?

  • Smooth surface → regular reflection
  • Rough surface → diffused reflection (no image formed)
• What is refraction?

  Refraction is the bending of light at the boundary between two optical mediums due to different optical densities.
• What causes light to bend during refraction?

  The change in speed of light due to different optical densities causes the path of light to bend.
• What happens when light travels from a less dense to a denser medium?

  It bends towards the normal, and the angle of refraction is smaller.
• What happens when light is perpendicular to a medium?

  Light will slow down but will not bend.
• How is the refractive index defined?


  η is defined as the ratio of the speed of light in vacuum to the speed of light in the medium.
• What happens to the refractive index as the density of a material increases?

  The refractive index increases as the material becomes denser.
• How does refraction affect the appearance of objects?

  Refraction causes objects to appear closer to the surface.
• What happens when light travels from an optically denser to a less dense medium?

  It bends away from the normal.
• How does the refractive index depend on the color of light?

  The refractive index is dependent on the color of light because different colors have slightly different speeds in any medium except vacuum/air.
• What are some uses of light in various fields?

  • Photosynthesis
  • Renewable energy
  • Health and medical treatments
  • Entertainment (laser shows, holography)
• What are the harmful impacts of light pollution?

  • Washes out starlight in the night sky
  • Disrupts ecosystems (affects nocturnal animals)
  • Adverse health effects
  • Disrupts migration patterns of birds
• What are some uses of infrared light?

  Infrared light is used in cameras to screen people, remote controls, and intruder alarms.
• What are the harmful effects of overexposure to infrared radiation?

  Overexposure can harm our eyes and skin and lead to climate change.
• What are some uses of ultraviolet light?

  Ultraviolet light increases vitamin D production, treats skin diseases, and sterilizes medical instruments.
• What are the harmful effects of overexposure to UV radiation?

  Overexposure can damage the retina, cause sunburn, and lead to skin cancer.
• What are the laws of reflection?

  1. The ray of incidence, ray of reflection and normal at the point of incidence all lie on the same plane
  2. The angle of incidence is equal to the angle of reflection.
• Speed of light in vacuum

  3.0 x 10^8 m/s
• What colour would a red rose and green leaf be under red light be?

  Rose >> red

  Leaf >> black
• When looking through a glass box at 90°, object will appear

  Nearer
• Only when light ray is perpendicular to medium then there is no refraction