State the main uses of polaroids.

Ans: Uses of Polaroids:

 1) Polaroids are used in motor car head lights to remove head light glare.

2) Used in three dimensional movie cameras.

3) They are used to produce and analyse               polarised light. 

4) They are used as filter in photography. 

5)They are used in window of aeroplanes to control amount of light.

6)  Used in polarising sunglasses (goggles) to protect the eyes from glare of sunlight.

7) They are used to improve colour contrast in old oil paintings.

8) They are used in calculators, watches, monitors of laptops which have LCD screens.

State methods to produce plane polarised light

 Ans: 

a) Reflection 

b) Scattering

c) Refraction 

d) Property of dichroism in calcite or quartz materials.

e) Polaroids

Explain the terms: i) Plane polarised light ii) Plane of vibration iii) plane of polarisation

 Ans:

A) Plane polarised light: The light waves in which vibrations of the electric field vectors are confined only to one plane are called polarised light.

B) Plane of vibration: The plane in which the vibrations of polarised light take place is called as plane of vibration.

C) Plane of polarisation: The plane perpendicular to the plane of vibration in which there are no vibrations of polarised light is called as plane of polarisation.

Why animals are preserved in science laboratory are kept in glass jars not in steel jars?

Because: We can't see, if animals preserved in steel jar. But in case of glass jars we can easily see animals and birds, whatever living things in lab. Those all are kept in glass jars only.

Because of nicely study about particular animals or plant.

And one important thing is that, in wet specimen glass jar, the liquid in which organism are kept is formaldehyde. So formaldehyde is corrosive to carbon steel.

So therefore, steel is not taken in use for preserved organism in jar.

Tricks and tips for activation of window 10 pro free easily

 Hello guys, in this article I am going to tell you about few and simple tricks and tips on how you can easily activate your window 10 pro free easily.

1) First of all, in your PC/ Laptop you have to go in search box option and type CMD, then you have to open CMD as an administrator and open.

2) In CMD type this code : i)  slmgr.vbs /ipk W269N-WFGWX-YVC98B-4J6C9-T83GX   then press Enter button.

3) Second code : ii) slmgr.vbs /skms kms.teevee.asia  then press Enter button.

4) And last third code : iii) slmgr.vbs /ato  then press Enter button.

And now your window 10 pro is successfully activated.

But in some cases, you will find your window 10 pro is not activated by this code, so it means that some files or folder  corrupted in your PC/ Laptop.

So that's why your window 10 pro is not activated.

So in that case : 1) First you have to go in setting and in setting you will find update and security option and then you have to go in Recovery option, so in the Recovery option you have to select Reset option and then you have to Reset your PC/ Laptop Completely.

When you click on Reset option then it will show two option i) Keep files and folders ii) Remove files and folder everything  so you go in Remove files and Folder.

After completing of Resetting of Pc/ Laptop then you have to update your window 10 pro and then uses above Code in CMD.

It will 💯 fix your issues !!!

A train cross a tunnel in 20 seconds at the entry of the tunnel velocity is 72 km/hr and the exist of the tunnel 36 km/hr. Find the length of the tunnel.

Solution:-

  t = 20 second.

 u = 72 km/hr  =   72×1000 / 3600 

                    u =   20 m/s   

  v = 36 km/hr = 36×1000 / 3600

                   v  =   10m/s

  a =  v - u / t

     =  10 - 20 / 20

     = -10 / 20

   a   = - 0. 5 m/s² 

v²   =  u²  + 2as

S    =  v² - u² / 2a

      =  (10)²  - (20)²  / (2 ) × (- 0.5)

      =  100 - 400 / -1

      = -300 / -1

 S   = 300 m

                            ∴ The length of the tunnel is 300m.

State applications of connectors used in optical fiber communication

1) Optical fiber connectors are used to join optical fiber where a connect /disconnect capability is required.

2) Optical fiber connectors are used in telephone exchange for customer premises wiring and in outside plant applications to connect equipment and fiber-optical cables.

3) Outside plant application may require connectors be located underground or on outdoors walls or utility poles.

Compare p-i-n and avalanche photodetector

 Pin diode:- 

1)  PIN photodiode does not have a high intensity electric field region.

 2) sensitivity is very low in PIN photodiode.

Avalanche photodetector:- 

1) Avalanche photodetector is a high-intensity electric field region.

2) sensitivity is very high in Avalanche photodetector.

Give selection procedure of compensation.

1) In general there are two situation in which compensation is required.

2) In 1st case, the system is absolutely unstable & the compensation is required to stabilize, if as well as to achieve a specified performance.

3) In 2nd case the system is stable, but the compensation is required to obtain the desired performance.

4) The system which are type 2 or higher are usually absolutely unstable, for these type of system clearly load compensator increase the margin of stability.

5) In type 0, type 1 system stable operation is always possible, if the gain if sufficiently reduced. In Such cases any of the 3 compensator lead, lag and Lead lag may be used to obtained the desired performance.