LIGHT (T.S. 1)

1 Marks Questions

Ques1. What is magnification of plane mirror?
Ques2. When a convex lens will act as magnifying Glass?
Ques3. The radius of curvature of a convex mirror is 20cm. What is its focal length?
Ques4. What is power of Lens of focal length of 20cm?
Ques5. Explain why a ray of light passing through the centre of curvature of a concave mirror, gets reflected along the same path.


2 Marks Questions

Ques6. Define the following terms in the context of spherical mirrors:
1) Pole
2) Center of curvature
3)Principal axis
4)Principal focus.

Ques7. The refractive indices of glass and water with respect to air are 3/2 and 4/3 respectively. If speed of light in glass is 2x108 m/s, find the speed of light in water.

Ques8. What is meant by power of a lens ? Write its S.I. unit.

Ques9. The linear magnification produced by a spherical mirror is +1/3. Analysing this value, state the type of mirror and  position of the object with respect to the pole of the mirror. Draw any diagram to justify your answer.

Ques10. A concave mirror produces three times magnified (enlarged) real image of an object 10 cm in front of it. Where is the image located?

3 Marks Questions(Attempt any 5)

Ques11. Draw a ray diagram to show the path of the reflected ray in each of the following cases.

A ray of light incident on a convex mirror:  

1...strikes at its pole making an angle θ theta from the principal axis.

2....is directed towards its principal focus.

3... is parallel to its principal axis.

Ques12. If the image formed by a mirror for all positions of the object placed in front of it is always virtual and diminished, state the type of the mirror. Draw any ray diagram in support of your answer.  

Ques13. An object is placed at a distance of 12 cm in front of a concave mirror. It forms a real image four times larger than the object. Calculate the distance of the image from the mirror

Ques14. A convex mirror used on a bus has a focal length of 200 cm. If a scooter is located at 100 cm. from this mirror find the position, nature and magnification of the image formed in the mirror.

Ques15. A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed?

Ques16. State the mirror formula for determining the focal length of spherical mirrors write the meanings of the symbols used An object is placed at a distance of 25 cm. from a concave mirror of focal length 15 cm. Calculate the distance of the image from the mirror.

Ques17. An object is kept at a distance of

(i) a/2   (ii) (3a/2) from a convex lens having focal length of magnitude (a) Draw ray diagrams showing the formation of images formed in the two cases.

5 Marks Questions(Attempt Any 2)

Ques18. Name the type of mirrors used in the following situations: 
A) Headlights of a car
B) Rear-view mirror of vehicle
C) Solar furnace
Support your answer with reason

Ques19. A convex lens has a focal length of 10 cm. At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm. away from the lens? What would be the size of the image formed if the object is 2 cm high? With the help of a ray diagram show the formation of the image by the lens in this case?

Ques20. One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answers experimentally. Explain your observations.

start text, i Principal focus.

D. P. P. Electricity

D.P.P. 1                                                2-July-2020

◾️Q 1. What is meant by electric current? Name and define its SI unit. In a conductor electrons are flowing from B to A. What is the direction of conventional current? Give justification for your answer.
A steady current of 1 ampere flows through a conductor. Calculate the number of electrons that flows through any section of the conductor in 1 second. (Charge on electron 1.6 X 10-19 coulomb).

◽️ANSWER:- ELECTRIC CURRENT :Electric current is the amount of charge flowing through a conductor per unit time. OR , 

We can say that ELECTRIC CURRENT is the rate of flow of charge.

➡️Its SI unit is AMPERE.

WHAT IS 1 AMPERE -> The current flowing through conductor is said to be 1 Ampere if 1 coloumb of charge passes through it in 1 sec.

Current = Charge / Time

1 Ampere = 1 coloumb / 1 second

➡️ In a conductor, if electrons are flowing from B to A, then the direction of conventional current is from A to B.

➡️Justification -> Because, the direction of conventional current is considered opposite to the flow of electrons. Electric current comprises of the flow of positive charge. So, its direction will be opposite to the direction of negative charges that are electrons.

1 Ampere equals 1 Coulomb per second. Since each electron has a negative charge of e≈1.602⋅10−19     C     $e\approx 1.602\cdot {10}^{-19}C$, the number of electrons per second for 1C is 1Ce≈6.242*1018 $\frac{1C}{e}\approx \mathrm{6.242*}{10}^{18}$.

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◾️Q2. Define 1 volt. Express it in terms of SI unit of work and charge calculate the amount of energy consumed in carrying a charge of 1 coulomb through a battery of 3 V.

◻️ANSWER  If 1 joule of work is done to carry 1 coulomb of charge from one point to another point , then it is said to be 1 V

Since we know that V=W/Q

so, put V = 3V And Q=1 c

by equating this in formula we get 3 j

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◾️Q3. How is an ammeter connected in a circuit to measure current flowing through it?

◽️ANSWER: The ammeter is connected ‘in series’. This means that it is connected such that all the current must flow through it.

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◾️Q4. A piece of wire of resistance 20 Ω is drawn out so that its length is increased to twice its original length. Calculate the resistance of the wire in the new Situation.

◻️ANSWER: Given resistance = R1 = 20 ohm

Let length of the wire = L

Therefore, new length of the wire = 2L

Since, when the length is doubled, cross sectional area of the wire becomes half.

Therefore, new resistance = R = 2L/ (A/2) =4L/A

R = 4 x 20 (since, L/A = resistance)

R = 80 ohm.