Wave Optics

 Sparkling short Answer Questions.

 1Q. What are the reasons to belive that light is a wave motion ?
 2Q. Can two wave-fronts cross one another ? Give reasons
 3Q. When monochromatic light travels from one medium to another then what happens.
 4Q. State the essential conditions for two light waves to be coherent.
 5Q. State the essential conditions to obtain sustained type of interference of light.
 6Q. Two independent light sources cannot act as cohrent sources. Why ?
 7Q. If the separation between the two slits is decreased in young double slit experiment
         keeping the screen position fixed,what will happen to the fringe width?
 8Q. How does the fringe width ,in Y D S experiment,change when the distance of separation
          between the slits and screen is doubled ?
 9Q. In Y D S E  if the distance between two slits is halved and distance between the two slits and
          screen is doubled,then what will be the affect on fringe width?
10Q. Two identical coherent waves,each of intensity Iare producing an interference pattern. Write
           resultant intensity at a point 1) constructive and 2) destructive interference.
 11Q. In YDSE lights of green ,yellow and orange are successively used.Write the fringe width in
            increasing order.
 12Q. In YDSE , if apparatus is immersed in water ,what will be effect on fringe?
 13Q. State the condition for diffraction of light.
 14Q. Diffraction is common in sound but not common in light waves ? Why?
 15Q. Why does the intensity of secondary maximum less as compared to the central maximum ?
 16Q. What is the basic difference between interference and diffraction of light ?
 17Q. A single slit diffraction pattern is completely immersed in water ,how is the width of central
           maximum affected ?
 18Q.  If yellow light is replaced by X-rays.how will the diffraction affected in single slit diffraction
             experiment ?
 19Q. Which special characteristic of light is demonstrated by polarization.
 20Q. Light waves can be polarised while sound waves(longitudinal wave) cannot.Why ?
 21Q. What is  polarizing angle?
 22Q. What is Brewster law ?
 23Q. Does the value of polarizing angle depend on color of light ?
 24Q. What is the angle of polarization, if 1) R.I =1.732 (2) angle of refraction (3) angle of polarizat
           - ion if slab is immersed into liquid of R.I =1.34 (4) if critical angle 45 degg.
 25Q. Write two simple uses of polaroids.
 26Q. Define,wavefront,wavelets,types of wave fronts and Huygen principle.

Sparkling questions

            SPARKLING SHORT ANSWER QUESTIONS

                                           PHYSICS                    

1Q. Can a body have zero velocity and finite acceleration?

2Q.Can a body have a constant speed but varying velocity?

3Q.Can a body have constant velocity but a varying speed? 

4Q. A particle is moving along a circular path of radius r what is the distance traversed in the 1/4^th of revolution what is the displacement?

 

5Q. If the displacement of a body is proportional to the square of time, state whether the body is moving with uniform velocity or uniform acceleration?

6Q. The displacement of a particle is proportional to the cube of time, state whether the body is moving with uniform velocity or uniform acceleration depends on time?

7Q. Can you use the equation of kinematics to find the height attained by an object projected upward with any velocity?

8Q. Can a relative velocity of two bodies be greater than the absolute velocity of either?

9Q. A ball is dropped from a top of tower and another ball is thrown at the same time. Which ball hit the ground earlier? Explain.

10Q. A car is moving on the level road where the rain is falling vertically downward. Why does the front wind screen get wet, whereas hind screen remain dry?

11Q. A swimmer wants to reach to a point just opposite on the other bank of river. How should he swim and why?

12Q. Can the direction of velocity change at every instant if acceleration is constant?

13Q. A projectile moves in a parabolic path without air resistance is there any point at which acceleration is i) parallel to the velocity and ii) perpendicular to the velocity. Explain

14Q. A hunter aims his gun and fires a bullet directly towards a monkey sitting on a distance tree. At the instant the bullet leaves the barrel of the gun, the monkey drops from the tree freely. Will the bullet hit the monkey. Explain?

15Q. A person sitting on a horse moving with constant velocity along the straight line throws himself vertically upward will the person return to the moving horse?

16Q. Two balls of different masses. Assuming air resistance to be same on each ball which mass falls earlier if they are simultaneously released from the same height? Explain with expression.

17Q. Why does a cricketer while catching a ball move his hand backward direction?

18Q. A man is at rest in the middle of a pond on perfectly frictionless iceberg. How can he get himself to shore?

19Q. A man drops his briefcase in elevator but it does not fall to the floor, is it possible?

20Q. When a heavy truck collides with a passenger car, the occupants of the car are more likely to be hurt than the truck driver, why?

21Q. A stone when thrown on a glass window smashes the window in the pieces but a bullet passes through a hole, why?

22Q. It is easier to pull then push a lawn roller why?

23Q. Why lubricants and ball bearing are used in the machine, explain how they reduce the friction?

24Q. Is a large brake on bicycle wheel more effective than a smaller one?

25Q. Why do we sleep on muddy road?

26Q. When a horse pulls a cart the cart pulls the horse backwards. Explain how the motion take place?

27Q. When a ball is thrown up the magnitude of its momentum decreases and then increases does this violate the law of conservation of momentum?

28Q. Can an object have eastward while experiencing a westward acceleration. Give example.

Answer key of physics numerical of exam2071(2014) grade 11,code110'D'

                            HSEB-GRADE XI

                              2071(2014)

                       PHYSICS. Sub code;110’D’

                                 Group-c

9.a.      Given that

             r=0.3/2=0.15m

             ρ=800kg/m3

             T=5x1o^-4N/m and , angle of contact(ѳ)=30◦.

As we know that.

              T=  r (h+r/3)ρg/2cosѳ

              or, h+r/3=2Tcosѳ/ r ρ g

               or, h =(2Tcosѳ/r ρ g)-r/3

               or, h= (2x5x10^-4cos30◦/0.15x800x10)-o.15/3

                       =( 8.66x1o^-4/1200)-0.05

                       =7.2x10^-7- 0.05

               So, h= -4.99x10^-2m.

The angle of contact is acute, so liquid must be rise in capillary tube but answer shows the fall of liquid .It is

 due to large diameter of tube0.3m.it should be 0.3mm.

  If someone uses the formula T=hρrg/2cosѳ

                                                 So,      h=7.2 X10^-7m

9.b. Given that

            M₁=4kg and m₂=40kg

             E₁=?      and   E₂=10J

Using,   E₁ /E₂ =m₂/m₁

              E₁=40/4 X10

                   =100J

Now,  ½ m₁v₁² =100

           V₁=(2 x100/4)^1/2

                =7.07m/s 

9.c. Given that, v=50km/hr=13.88m/s and r=200m

         Tanѳ= v²/rg

          Ѳ =tan^-1(v²/rg)

              =tan^-1(13.88x13.88/200x10)

              =5.5⁰

9.d.  T= 2X3.14 Xr/6.2 x1ooo=10^-3r sec. and ,a=v²/r=(3.8x10⁷/r) m/s. where r=radius of earth satellite.

10.a. first correct the question, how much temp of  source be raised so that the efficiency is increased by

15% at constant temp of sink at 27^0C

             Given that

                η  = 25%  T₂  =27+273=300K

                So,  η = (1 – T₂/T₁)

                      25/100 =(1-300/T₁)

                          T₁ =400K

          Now, η =25+15=40%

           So,  40/100 =( 1-300 /T₁^’)

                       T^’₁ =500K

Increase in temp= 500 -400 =100k

10.b.  Given that , p=1.5kw=1500w

                                 l =0.3m and r =0.04m

         Using , P=σ A T⁴

                                T=( P/σ A)^1/4

                        = ( 1500/5.67X10^-8X2X3.14X0.04X0.3)^1/4

                       =769K(aprox)

10.c.  Using,  W=Q

                      mgh =ml_i

                      =3.36 x10⁴

                      =33.6 x1o³m

                      =33.6km

11. Given that, R =0.4 m so, f =0.2m =20cm

                            m  =v/u=-3 (for erect and virtual image)

     Using ,1/u +1/v =1/f

                1/u -1/3u =1/20

                    u  =13.33cm˃

12. Given that, C₁=1µF

                             C_{2 =}2µF

                             C₃ =3µF

  For series, 1/C_S = 1/C_{1 +} 1/C₂ +1/C₃

                         C_{S =}6/11µF

And ,for parallel, C_P= C₁+C₂+C₃

                                   =1+2+3=6µF

       C_S/C_P =1/11

    C_{P =}11C_S;   C_{P greater than Cs}  

ANSWER OF NUMERICAL QUESTIONS.EXAM 2071 PHYSICS CODE210'D'

                                  HSEB-GRADE XII

                                    2071(2014)

                                PHYSICS;SUB CODE:210'D'

        Answer of numerical questions.

9Q.a.              F=3.75 x1O-24 N

      b.              i=1.2 A and, pd across 4ohm(v)=4.8v

      c.              emf induced=1.57 volt

10Q.a.         insufficent data.but some one using the value of

                 work function,say ,w =2ev for potasium then

                   KE=2.3 ev and, stopping potential=1.44v

     b.         BE per nucleon=7.07Mev

     c.          radius=0.75mm

11Q.     Velocity at o0c=318.6m/s

12Q.       no.of rulings per mm=406

SCIENCE OF TOPS

	Why does a top spin?
	Tops spin because of the basic laws and principles of physics.

Inertia	The tendency of matter to remain at rest (or keep moving in the same direction) unless affected by some outside force or forces. When you wind up a top, you are storing energy in it. As the top is thrown, the energy is slowly released and the itertia keeps the top moving until acted upon by outside forces. In the case of the top, these forces are gravity and friction.
Gravity	The force that tends to draw all bodies in the earth's sphere toward the center of the earth.
Friction	The resistance to motion of surfaces that touch. In the spinning top there are two types of friction: direct friction of the tip with the spinning surface and air friction with the surface of the top. The sharpness of the tip, the smoothess of the spinning surface, and smoothness of the top's surface determine the amount of friction the spinning top will encounter. The less friction, the longer the spin.
Centrifugal Force	Forces tending to make rotating bodies move away from the center of rotation. This principle states that a body (the top) rotating rapidly about its axis will tend to resist outside influences (gravity). Actually, a top remains upright because centrifugal force pulls inward on the top, keeping the vertical axis of the top perpendicular to the horizontal axis of the ground.

As the spinning top slows down, friction and gravity try to tip it over. These forces are resisted by the top's inertia. As the top continues to slow, the crown of the top begins to tip at an angle. The crown moves as it travels in circles and rotates on its axis trying to right itself. This is call precess. As the speed is slowed further by gravity and friction, the top will continue to precess until such time as gravity and friction outweigh the inertia and the top topples and falls.

CLASS TEST OF BIO B

                        NATIONAL INFOTECH
 

CLASS TEST                                                                                        CLASS-11

TOTAL MARKS- 20
NOTE: Answer all the questions.

 Q1. Prove that 3p=ρc² , where symbols have usual meaning.

 Q2. Describe the necessary theory to determine thermal                          conductivity of a metal bar.

 Q3. State and explain newton’s law of cooling.  Derive an equation        for specific heat of liquid.

 Q4.a) What is temperature of vacuum?

      b) Define absolute temperature?

      c) What happens when a metallic block with hole is heated?

      d) Why does food cook faster in a pressure cooker than in an                open vessel?

                     ANSWER KEY HSEB 2070[2013]

                                        PHYSICS. SUB. CODE 110' D'

                                                                                                                                                                                                                       

                                                 GROUP 'C'

 9 Q.( a)     F=7.2 N and F =8.28 N

       (b)     n =67.5 rpm

       (c)     w =8.35 x 10^-3 J

       (d)     v =3.77 m / s and  a =94.6 m /s²

 10 Q .(a)    c =528.57 J/kg /k

         (b)    k= 178.34 w /m/k or, k= 0.42 cal /s /cm/⁰C

         (c)     Efficiency (n) =30 %

 11 Q  angle =0.0091 radian

 12 Q.  V =604 v and E=1.2 x 10⁵ v/m