Telangana SCERT Class 9 Physical Science Chapter 4 Solution – Refraction of Light at Plane Surfaces. Here in this post we provides Class 9 Physical Science Refraction of Light at Plane Surfaces Telangana State Board Solution. Telangana State Board English Class IX Medium Students can download this Solution to Solve out Improve Your Learning Questions and Answers.
Telangana State Board Class 9 Physical Science Chapter 4 Refraction of Light at Plane Surfaces Solution:
CHAPTER: – 4.
(Refraction of Light at Plane Surfaces)
Exercise: –
I.) Reflections on concepts
1) The speed of the light in a diamond is 1, 24, 000km/s. Find the refractive index of diamond if the speed of light in air is 3,00,000 km/s. (AS1)
Ans: – The refractive index of diamond to air
= (speed of the light in air /speed of the light in diamond).
= 300000km/s / 124000km/s
= 2.4.
So, the refractive index of diamond is 2.4.
2) Refractive index of glass relative to water is 9/8. What is the refractive index of water relative to glass?
Ans: – The refractive index of glass relative to water= 9/8,
As we all know that refractive index of water relative to glass is = (1/refractive index glass relative to water).
So, refractive index will be (1/9/8) = 8/9.
3) The absolute refractive index of water is 4/3. What is the critical angle?
Ans: – From the formula it is known that, N= 1/ Sin C or, Sin C=1/N.
Then, Sin C =1/ 4/3.
Sin C=3/4
Sin C = Sin48.59°.
C= 48.59°.
4) Determine the refractive index of benzene if the critical angle of benzene with respect to air is 42°.(AS1)
Ans: – critical angel = C =42°
Then refractive index of benzene will be = 1/Sin C
= 1/Sin42°
= 1.5.
5) Explain the formation of mirage? (AS1)
Ans: – Mirage is an example of an optical illusion. The reason behind the formation of its total internal reflection of light. We see this phenomenon on a humid sunny day where we can see water at a distance but after going closer there is nothing.
6) Explain the refraction of light through a glass slab with a neat ray diagram. (AS5)
Ans: –
7) Why do stars appear twinkling? (AS7)
Ans: – There are different atmosphere layer where various particles of different layer present as the light rays passes through this layer as a result of that the light rays get reflected. And after that we see stars appear twinkling.
II.) Application of concepts
1) A light ray is incident on air-liquid interface at 45°and is refracted at 30°. What is the refractiveindex of the liquid?
Ans: – From formula we know refractive index = Sin i/Sin r
It is given that, i= 45° and r= 30°
So, refractive index = Sin45°/ Sin30 = 1.14
2) In what cases does a light ray not deviate at the interface of two media?(AS7)
Ans: – The ray would not deviate as –(1) if refractive index is equal (2) if the incidence ray strikes at incidence point.
3) Place an object on the table. Look at the object through the transparent glass slab. You will observe that it will appear closer to you. Draw a ray diagram to show the passage of light ray in this situation. (AS5)
Ans: –
4) Why does a diamond shine more than a glass piece cut to the same shape? (AS7)
Ans: – The refractive index of diamond is higher than the glass because of that in diamond more total internal reflection takes places. As a result, there is seen diamond shine more than the glass piece.
III.) Higher Order Thinking Questions
1) Why is it difficult to shoot a fish swimming in water? (AS1)
Ans: – The refractive index is different in water and air so as a results of that we see that the fish which is present in any swimming pool seems to appear closer but in reality, is not as close as that. So, for this reason we see difficulty to shoot a fish in swimming.
2) Explain why a test tube immersed at a certain angle in a tumbler of water appears to have a mirror surface for a certain viewing position?
Ans: – As light rays in water while strike the test tube made an angel which is greater than critical angel.So, after this phenomenon total internal reflection takes places as a result the rays come to our eyes which seems from the surface of it.
3) When we sit at a camp fire, objects beyond the fire are seen swaying. Give the reason for it.
Ans: – The denser air in the time of camp fire causes the refraction the light beyond the fire. As a result, we see the object light after reflection there we see swaying.
MULTIPLE CHOICE QUESTIONS.
1.) Which of the following is Snell’s law.
a) n1 sin i = sin r/ n2 b) n1/n2 = sin r / sin i
c) n2 / n1 = sin r / sin i d) n2 sin i = constant.
Ans: – option (b).
2.) The refractive index of glass with respect to air is2. Then the critical angle of glass-air interface is …………..
a) 0o b) 45o c) 30o d) 60o.
Ans: – Option ©.
3.) Total internal reflection takes place when the light ray travels from……………
a) rarer to denser medium b) rarer to rarer medium
c) denser to rarer medium d) denser to denser medium.
Ans: – option (c).
4.) If the angle of incidence is equal to critical angle, then the angle of refraction is
a) 0o b) 20o c) 90o d) 180o.
Ans: – option (c).
5.) Mirage is a best example for the phenomenon of
a) Reflection b) Refraction c) Total internal reflection d) Shift.
Ans: – Option (c).
6.) Refractive indices of Ice, Benzene, Ruby and Kerosene are 1.31, 1.50, 1.71 and 1.44respectively. In which of the above media, light travels showly?
a) Ice b) Benzene c) Ruby d) Kerosene.
Ans: – option (c).
7.) The relative refractive index of water with respect to air is 4/3. Then relative refractive index of air with respect to water is
a) 4 b) 3 c) 4/3 d) ¾.
Ans: – option (d).
8.) In an experiment to trace the path of ray through a glass slab, Shiva traced as shown in the figure. The teacher asked him to identify the emerging ray. Whichof the following would Shiva identify?
a) AB b) BC
c) CD d) N2.
Ans: – option (c).
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