Question

please give the reason

Answer 1

@Mashy

Answer 2

finger is placed in the centre of torch
then also 2 small coherent source appears on the shadow of finger
why?

Answer 3

if u'll want try it :)

Answer 4

@ganeshie8

Answer 5

@Compassionate

Answer 6

i did not understand

Answer 7

You are seeing some of the effects of the wave nature of light. Light does bend around obstructions slightly, just as all waves do. This is called diffraction. It's why you can hear someone calling you even when they are around a corner (sound waves bend around a corner). These effects are proportional to the size of the wave, which is very small for light. For this reason, you do not see diffraction of light except on very small scales, like when things are very close to your eye, or when you look through a microscope. The same thing happens when light tries to fit through a very small slit--when that slit gets close to the distance of a wavelength of light, then suddenly it diffracts a whole bunch.

Answer 8

mm im not clear its ok
thx 4 giving time :)

Answer 9

I am fairly sure this is not due to diffraction the aperture size is too large.

Is this a standard torch? maybe I'll try to reproduce it.

You could begin to trace the rays back from the hot spot by placing a needle or point in the spot then moving it and keep the shadow in the spot...

Answer 10

@nirmalnema @Abhisar

Answer 11

@nincompoop @Preetha

Answer 12

can you take a photo without the finger?and attach?

Answer 13

mmm now im having dinner

Answer 14

how does that drawing explain the two bright spots? :P

Answer 15

Driffraction not for sure, the width of the finger is way larger than lamba
mm @Mashy you're right now i've see I've misunderstood the picture :)

Answer 16

Maybe you see on the torch that little bump? it could be that which reflect down the beam

Answer 17

The light cannot fade of that quickly unless there is some obstacle

look at the spots.. it just fades off into the darkness (of the shadow) so quickly.. i hardly see any gradient..

Photoshop? :P

Answer 18

or he/she is wearing something on his/her finger.. like two leds.. :P

Answer 19

it would be much better if you took a video of u inserting ur finger in the path of the light.. and maybe uploading it on utube and passig the link.. that would be interesting to see nd easier to discuss

Answer 20

i hope it would have been possible

Answer 21

can u take another picture.. ? with out the finger

and one more with ur finger half way into the path of light?

Answer 22

i'll see

Answer 23

btw can u explain me escape velocity?

Answer 24

The min. velocity with which u need to throw a projectile such that it escapes the gravitational pull of that planet.. For earth its roughly 11.2 km/s.. moon is about 5 times lesser about 2.4 km/s..

Answer 25

critical vel.?

Answer 26

dunno what u mean by that..
but i think u are referring to what we usually call as orbital velocity.. the velocity with which u need to shoot a projectile tangentially, such that it orbits the planet in a perfect circular path

Answer 27

Maybe his finger is made of neutron star

Answer 28

can anyone give me difference between orbital and escape velocity

Answer 29

@Armi thats the worst reasoning so far xD

u should be able to figure out the differences urself now @rvc

Answer 30

@Armi IF U WANT TO HELP THEN PLS
nothing else

Answer 31

@Abhisar will u help me?

Answer 32

@rvc
Escape velocity is not the same as orbital velocity.

The force of gravity between 2 bodies is
\[F= \frac{ GMm }{ r ^{2}}\]

The energy required to move a distance delta r is f delta r

If you want to 'escape' from a gravitational pull you must have sufficient energy to move to a 'large distance' (essentially infinite distance) from the body.

The energy to do this is

\[Energy= \int\limits_{0}^{\infty} Fdr\]

The kinetic energy of a body is 0.5mv^2

So to escape grvitaitonal field

\[\frac{ mv ^{2} }{ 2 }=\int\limits_{0}^{\infty}\frac{ GMm }{ r ^{2} }dr\]

If a body has the initial velocity greater than this value for v then it will not 'fall back' to the attracting body. If it's velocity is less then it will eventually return to the body under gravitational pull

Answer 33

In reality you have to take an initial value of r (e.g. radius of earth) ( i.e. The integral is from r0 to infinity)

because other wise at r=0 the force is infinite....

Answer 34

The angular displacement of second hand of a clock in 10s is equal:
30degree , 60degree , 45degree ,90degree

Answer 35

@aayushi.somani @Mashy

Answer 36

please ans

Answer 37

that is easy..

in 60 seconds.. the second hand takes one full rotation.. so it covers 360 degrees
so in 10 seconds.. what u think?

Answer 38

60

Answer 39

correct

Answer 40

thanks!

Answer 41

angular speed of sec hand ?

Answer 42

@Mashy

Answer 43

u should be able to calculate that now :P.. whats the formula for angular speed?

Answer 44

i got it!!!!!!!