12. Light Flashcards
Laws of reflection
1) Incident ray, reflected ray and normal lie on the same plane
2) angle of incidence= angle of reflection
Types of reflection
1) on smooth surface, the reflected ray are parallel to each other
2) On rough surface, irregular and disorder reflection
Characteristic of mirror images:
1) mirror image and object are equally far from the mirror
2) mirror image and object have the same size
3) Mirror image are laterally inverted and upright
Law of refraction
1) Incident ray, reflect ray and normal lies on the same plane
2) For 2 given media, ratio of (sin) is constant
Refraction formula
sin i/ sin r= constant
Refractive index
index= speed of light in vacuum/ speed of light in medium
What is a principal axis?
It is perpendicular to the lens, it passes through centre of the lens
Optical centre
Point on principal axis that is midway of lens’s surface
principal focus point
point on principal axis where all ray are parallel to principal axis
Focal plane
the plane perpendicular to the principal axis where all ray is parallel to principal axis
Focal length
distance between optical centre and principal focus point
At which distances, is the image formed diminished
1) u= infinity
2) u is more than 2f
Where is distance of object when image is same size?
u=2f
Where is the distance when the image is magnified ?
u is between f and 2f
Which 2 distances is when image is virtual, upright and magnified?
- u=f
- u lesser than f
