Skip to main content

Example questions from human eye and colourful world

 HUMAN EYE AND COLOURFUL WORLD

EXAMPLE QUESTIONS:

 

1  1) Light of wavelength λ1 enters a medium with refractive index n2 from a medium with refractive index n1. What is the wavelength of light in second medium?

ANS:  we know, refractive index is inversely proportional to wavelength.

            n∞1/ λ

ð n1/n2= λ2/ λ1

ð λ2=n1 λ1/n2

 

2  2)  If a white sheet of paper is stained with oil, the paper turns transparent. Why?


ANS: we can get so many answers for this question because there may be multiple reasons for this. But i will suggest one best answer for this.

A white sheet of paper consists of cellulose. The refractive index of cellulose is very near to the refractive index of oil. so, it turns transparent.

 

3    3) A light ray falls on one of the faces of a prism at an angle 40o so that it suffers angle of minimum deviation of 30o. Find the angle of prism and angle of refraction at the given surface.


ANS: To answer this question i suggest you to revise the derivation part of finding refractive index of prism.

Given i1=400

            D=300

At minimum deviation i1=i2=i  and r1=r2=r

ð A+D=2i

ð A=2i-D

ð A=2(40)-30

ð A=500  (angle of prism)

Also we know, d= (i1+i2)-(r1+r2)

ð D=2i-2r  (at minimum deviation)

ð 2r=2i-D

ð r=[2i-D]/2

ð r=[2(40)-30]/2

ð r=50/2=250

 

4)     4) The focal length of a lens suggested to a person with Hypermetropia is 100 cm. Find the distance of near point and power of the lens.

ANS:

      Given f=100 cm

We know focal length of hypermetropia is given by

f=25d/(d-25), where d is the near point.

ð 100=25d/(d-25)

ð 100d-2500=25d

ð 75d=2500

ð d=2500/75=33.33 cm

 

5    5) A student sitting in last bench of a class room cannot see the black board clearly. What is the name of the eye defect he has? What lens is suggested for this defect?


ANS: As the student cannot see far objects he has the defect of short sightedness which is known as myopia. To correct this defect a bi concave lens is suggested.

 

6   6) A person in a car cannot see objects in the rear view mirror of the car. What is the name of the eye defect he has? What lens is suggested for this defect?


ANS: As the person cannot see near objects, he is suffering from far sightedness which is known as hypermetropia. A bi convex lens is used to correct this defect.

7)7)    What type of lens is suggested for the people suffering from presbiopia?

Draw the symbol of this lens.

ANS: For the people suffering from presbiopia a ‘bi focal lens’ is suggested. It is represented symbolically as 

Bifocal lens symbol

The upper portion is concave and the lower portion is convex.



thank you

Labels:

Comments

Post a Comment

Please don't post spam links in comments

Popular posts from this blog

SPECIFIC HEAT CAPACITY AND HEAT CAPACITY

  Specific heat capacity    Specific heat capacity can be defined as it is the amount of heat energy required to raise the temperature of unit mass of a substance through one degree Centigrade.    Different bodies have different values of their specific heat depending upon their nature. Some of the examples are given below   How we can derive formula for specific heat?   Based on a simple activity we can derive a formula for specific heat.  Take two beakers and name them as A and B. Fill the two beakers with some water. Let us assume that the mass of water in both the beakers be 1 kg.    And the water present in both the beakers is at room temperature.    Let us assume that we have to raise the temperature of water in beaker A to 50 0 centigrade. And we have to raise the water in beaker B to 70 0 Centigrade for a given constant time.   In order to do so definitely we have to supply more heat ene...
Post a Comment
Read more

Rules to draw ray diagrams & sign convention rules for spherical mirrors

  RULES TO DRAW RAY DIAGRAMS FOR SPHERICAL MIRRORS                                                                            Rule 1: The ray passing parallel to principal axis, after reflection passes through focus (or appears to be coming from focus in case of convex mirror) Rule 2: The ray passing through Focus (or appears to be passing through focus in case of convex mirror), after reflection becomes parallel to principal axis.                                                        Rule 3: The ray passing through principal axis comes back in the same path after reflection.      ...
Post a Comment
Read more

prism and refractive index of prism

  PRISM:   A prism is a transparent medium separated from the surrounding medium by at least two plane surfaces which are inclined at a certain angle in such a way that, light incident on one of the plane surfaces emerges from the other plane surface. Consider a triangular glass prism. It contains  two triangular bases and three rectangular plane lateral surfaces. These lateral surfaces are inclined to each other. Let us consider that triangle PQR represents outline of the prism where it rests on its triangular base.       Let us assume that a light ray is incident on  the plane surface PQ of a prism at M as shown in figure. Draw a perpendicular to the surface at M. It becomes a normal to that surface. The angle between the incident ray and normal is called angle of incidence (i 1 ). The ray is refracted at M. It moves through prism and meets the other plane surface at N and finally comes out of the prism. The ray which comes out of the surfa...
Post a Comment
Read more