REFLECTION OF LIGHT AT CURVED SURFACES

REFLECTION OF LIGHT AT CURVED SURFACES

1.     Convex mirror vs concave mirror:

2.     Real Vs virtual images

SNO	REAL IMAGE	VIRTUAL IMAGE
1	Can be caught on the screen	Cannot be caught on the screen
2	Real image is formed when all reflected rays meet in front of the mirror	Virtual image is formed when reflected rays are extrapolated and appears to meet at a point.
3	Formed in front of the mirror	Formed backside of the mirror
	Real images are always inverted	Virtual images are always inverted

3.     consequences if spherical mirrors were not known to human beings

a)     1) Spherical mirrors are used in different ways in our daily life.
2) Convex mirrors are used in every place like hospitals, hotels, stores, apartments, roads, ATM's, computer monitors. Etc

b)     Convex mirror is used as a rare view mirrors in vehicles

c)      Convex mirrors are used in sun glasses.

d)     concave mirrors are used by ENT doctors to see inner parts of mouth

e)     Also used in Car head lights.

4.     How do you get a virtual image using a concave mirror?

A)   Virtual image is formed behind the concave mirror when an object is placed in               

  between focus and pole.

 

5.Rules for sign convention?

A) All the distances are to be measured from pole only

     The distances measured in the direction of incident ray is taken +ve

     The distances measured opposite to the direction of incident ray is taken – ve

     Height of the object / height of the image above the principle axis is taken and +ve and below the principle axis is taken as -ve.

Note1: focal length (f) and radius of curvature(R) are -ve for concave

Note2: focal length (f) and radius of curvature(R) are +ve for convex

6 Draw suitable ray diagrams by which we can guess the position of image formed by concave &   convex mirrors?

A)    A ray passing parallel to principle axis moves through the focus point

B)    A ray passing through the focus point moves parallel to principle axis

C)    A ray passing through the pole/centre of curvature (normal) , doesn’t deviate its path

7) A convex mirror with a radius of curvature of 3m is used as a rear view in for a vehicle. If a us is located at 5m from the mirror then find the position and nature of the image?

As per sign conventions;

R= +3 m, 

Object distance (u)= -5m

V=?

F= R/2

  = 3/2
  = 1.5 cm

FORMULA USED= 1/f = 1/v = 1/u

 Substitution:

 1/1.5 = 1/-5 + 1/ v           magnification: m= height of the image / height of the object                                                                             m  =     - v/u = - 1.15/-5  = 0.23 m

   V= +1.15 m

Nature of the image:

It is a virtual image formed back of the convex mirror

It is an erect image and diminished to 0.23 times the object size.

8) which kind of mirrors are called spherical mirrors?

 a) The mirrors which are a part of hollow glass sphere and which have curved end are called spherical mirrors.

Examples: concave and convex.

9) what is magnification ?

M= height of the image / height of the object

                               m  = - v/u

Important notes:

1)     Angle of incidence and angle of reflection are equal for curved/spherical surfaces

2)     Spherical mirrors in our daily life: spoon, spectacles, door knobs, cooking vessels, shaving mirrors, reflectors in head lights of automobiles, dentist mirror, cookers. Etc

3)     Converging mirror: concave mirror

4)     Diverging mirror: convex mirror, i.e why it is used as a rear-view mirror

10) find the image distance when an object is placed infront of a concave mirror whose R= 8cm.

F= R/2  =  8/2  = 4cm

U= 10cm

V=?

FORMULA USED==1/f= 1/u + 1/v

 Substitute the values in above equation

 = 3/20

V(image distance) = 6.66cm

Important note: don’t forget to learn experimental activities.

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