Question

when a thermal sensor is covered with a transparent glass it blocks the thermal radiations and gives a full blue screen ...HOW?

Answer 1

glass may be transparent in visible light...

.. But they usually block infra-red radiation, which thermal sensors use to measure heat

Answer 2

how does it block?

Answer 3

@Vaidehi09 @ujjwal

Answer 4

@mathavraj sry...i don't have much knowledge about this.

Answer 5

will read about a lil' and come back to u.

Answer 6

its ok vaidehi..thanks for ur concern:)

Answer 7

any substance ... either reflects, absorbs, or lets through radiation of any particular frequency

glass is designed to reflect infra-red radiation ... for energy saving purposes

Answer 8

i don't have a more detailed knowledge to explain absorption bands ... or whatever properties are involved

Answer 9

thanks pax

Answer 10

anyone please explain this..iam confused

Answer 11

wait a min..something clicd my mind

Answer 12

If you were a mosquito ... or a snake that can see in infra-red ... the glass would not appear transparent.

Answer 13

i hav read in my text book during school that green houses(place to grow plants)glass is used to trap ir rays and provide heat during night

Answer 14

yea, i've also read that.

Answer 15

exactly! your question is about green house phenomena.. Glass transmits visible light but blocks infrared thermal radiation from escaping. This amplifies the heat trapping effect.

Answer 16

so we know it blocks thermal radiations. but why blue screen?

Answer 17

in a thermal camera cold substances appear blue

Answer 18

but y is glass so special?

Answer 19

Not much idea about it. So, i chose not to reply earlier.

Answer 20

maybe u'll have to go deeper....at the molecular level. see what happens at that scale. what differentiates a material from an another at that level. and prob u'll be able to answer that ques.

Answer 21

i was thinkin the same

Answer 22

glass is amorphous,isotropic,and a supercoold liquid

Answer 23

it polarises light...tats wat i kno

Answer 24

sorry. i can't be of much help here. i have limited knowledge in this domain.

Answer 25

ok its ok...

Answer 26

@agentx5 pls help me

Answer 27

Actually what @PaxPolaris and @ujjwal have been saying is absolutely correct. We often use thermal imaging cameras in burn test in fire & safety engineering (mock up of a room, then set it on fire according the the experiment's procedure then observe & record results), and an portal models have come down in price enough that several city fire departments can now afford to buy them (you can see them on show in the FDIC conference that is typically held in Indianapolis, IN, USA which draws professionals from as far away as Australia)

You have to understand @mathavraj, sometimes the reason it's showing up as a solid, unshaded block of color on the screen is because of how the software is interpreting. You see to the software, it's reading the sensor output as a zero or divide-by-zero type of error so it just goes to a preset else function of the conditional that says it's going to be a solid blank color.

In truth, glass has just the right crystalline width (even though it is a supercooled liquid technically it still exhibits properties of crystals, as paradox if you will because it has some of both) that it can absorb infrared light. It should also be noted that depending on the way the glass was manufactured, shatter-resistant coatings, and impurities in the silicon dioxide. Though quartz glass in theory contains only silicon and oxygen, industrially produced quartz glass DOES contain impurities. Do this impurities also have an effect? Yes.

Mathavraj, based on the knowledge of the wavelength of the infrared light (inverse of the frequency) you should definitely be able to tell the spacing in the quartz crystal. And if you have an accurate way to measure this you can even tell different types of glass from one another, a technique used in forensic science investigations on rare occasion.

Answer 28

using braggs law rit..2d=n*lambda*sin theta