Physics 2008 | Study Mode

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Question 21

I. Total internal reflection of light.
II. Conservation of light energy.
III. Relative motion of the earth, sun and moon.
IV. Rectilinear propation of light.
which of the above is a phenomenon of total solar eclipse?

A

I and IV only

B

II and IV only

C

I and III only

D

III and IV only

Explanation

Share Answer Due to rectilinear propagation of light we have ecslipse which occur as a result relative motion of the earth, sun and moon

Correct option: D

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Question 22

An object of height 4cm is placed in front of a cuboid pinhole camera of size 6 cm. if the image formed is 2 cm high, how far is the object from the pinhole?

A

3.0 cm

B

8.0 cm

C

12.0 cm

D

16.0 cm

Explanation

Share Answer Magnification = (image height)/object height
= (lenght camera)/object distance from pin-hole
(2)/4 = (6)/X
X (4 x 6)/2 = 12 cm

Correct option: C

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Question 23

An object of heights 5 cm is placed at 20 cm from a concave mirror of focal length 10 cm. the image height is?

A

20 cm

B

15 cm

C

10 cm

D

5 cm

Explanation

Share Answer (1)/V + (1)/U = (1)/f
(1)/V + (1)/20 = (1)/10
(1)/V = (1)/10 - (1)/20 = (2 -1)/20 = (1)/20
V = 20 cm
mag = (image height)/object height = (v)/u
(X)/5 = (20)/50
X = 5 cm

Correct option: D

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Question 24

Convex mirror are used as driving mirrors because images formed are?

A

erect, virtual and diminished

B

erect, real and diminished

C

erect, virtual and magnified

D

inverted virtual and diminished

Explanation

Share Answer Image formed by convex mirror is always erect, virtual and diminished

Correct option: A

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Question 25

An object placed at the bottom of a well full of clear water appears closer to the surface due to?

A

diffraction

B

reflection

C

refraction

D

polarization

Explanation

Share Answer Real depth and apparent dept is due to refraction

Correct option: C

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Question 26

In the microscope, the eyepiece lens merely acts as?

A

an inverter

B

a refiner

C

a diminisher

D

a magnifier

Explanation

Share Answer The basic function of microscope is magnification

Correct option: D

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Question 27

An observer with normal eyes views an object with magnifying glass of focal length 5 cm. the angular magnification is?


[least distance of distinct vision D = 25 cm]

A

-6

B

-5

C

5

D

6

Explanation

Share Answer Angular magnification, M = ((D)/F + 1) where D is least distance of distinct vision
M = ((25)/5 + 1) = -6

Correct option: A

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Question 28

A short chain is sometimes attached to the back of a petrol tanker to?

A

generate more friction

B

ensure the balancing of the tanker

C

caution the driver when overspeeding

D

conduct excess charges to the car

Explanation

Share Answer The friction between the tanker and air creates charges which the chain conducts to the ground.

Correct option: D

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Question 29

An electric generator has e.m.f. of 240 V and an internal resistance of 1 if the current supplied by the generatoris 20A when the terminal voltage is 220 V, find the ratio of the power supplied to the power dissipated?

A

11:1

B

1:11

C

12:11

D

11:12

Explanation

Share Answer Power supplied = IE = 20 X 240 = 4800 W
Power dissipated = IV = 20 X 220 = 4400 W
(Power supplied)/Power dissipated = (4800 W)/4400 W
= (12)/11

Correct option: C

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Question 30

A generator is on daily use and in the process, ten 60 W and five 40 W tungsten bulbs are on for the same time interval. the energy consumed daily is?

A

0.96 kWh

B

19.2 kWh

C

9.60 kWh

D

19.20 kWh

Explanation

Share Answer Energy consumed = power x time
= (60 W x 10 + 40 W x 5) x 24 h
= (600 W + 200 W ) x 24 h
= 800 W x 24h = 19200 w h
= 19.2 kWh

Correct option: B

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