Transfering heat from a distance

[Billy121]

Is it possible to heat an object from a short distance, perhaps a 1 metre distance without using infra red or ultraviolet? Is it possible to use another part of the spectrum to transfer heat? 

 

Thanks again. 

[Strange]

Microwaves are fairly commonly used for this purpose.

[swansont]

Terminology detail: It would not necessarily transfer heat, as heat is specifically from a temperature difference.

Any EM radiation would suffice. In “National Treasure” they use a green laser to do this. It’s a matter of efficiency - you prefer that the target absorb and not reflect.

[Billy121]

Is it possible to make a small unit which fires a focused beam of RF to heat an object from about 1metre away. Doesn't need to heat it much, just a modest difference. If not, is there any other method for achieving this whilst ideally avoiding IR and microwaves. Thanking you. 

[Strange]

!

Moderator Note

Merged with existing thread

 

[studiot]

Moving this lost the post I just made.

In general the loner the wavelength the harder it is to focus and the alrger the emitter will be.

Since you don't want much heat, what is wrong with a laser, the one out of a CD player will do.

[Billy121]

I want something invisable and undetectable ideally. Thanks for all the wonderful replies and help. 

[Strange]

57 minutes ago, Billy121 said:

I want something invisable and undetectable ideally.

So what is wrong with infra-red?

Radio waves are likely to pass through the object (depending what it is made of and what the frequency of the radio waves are). 

[Billy121]

Infra seems to show up on the most basic of cameras, just a normal iPhone show it very clearly. 

[Strange]

1 minute ago, Billy121 said:

Infra seems to show up on the most basic of cameras, just a normal iPhone show it very clearly. 

Well, anything absorbed by the target is quite likely to also be absorbed by the sensor in a camera.

But that may depend on what the target is made of. If it has very different absorption characteristics than a silicon chip, then you might be able to find a specific frequency which will affect one but not the other.

[Billy121]

Thank you for all the replies, it genuinely appreciated. The target is plastic, cellulose acetate plastic to be precise. 

[Strange]

7 minutes ago, Billy121 said:

Thank you for all the replies, it genuinely appreciated. The target is plastic, cellulose acetate plastic to be precise. 

That is transparent (to visible light) in its pure form. So it may depend on other substances mixed with it to dye it or change the mechanical properties.

[studiot]

2 hours ago, Billy121 said:

I want something invisable and undetectable ideally. Thanks for all the wonderful replies and help. 

This is homework which implies it is a learning exercise of some sort.

Part (some say the best part) of all such learning excercises is to find out what you can't do as well as what you can.

[swansont]

2 hours ago, Billy121 said:

Infra seems to show up on the most basic of cameras, just a normal iPhone show it very clearly. 

Only NIR, unless you have a thermal imaging camera. Si can’t detect wavelengths longer than ~1.1 microns.

But yes, you could make a directional antenna for RF. It could be a parabolic dish, which would have to be several meters in diameter

[Billy121]

Infra seems to show up on the most basic of cameras, just a normal iPhone show it very clearly. 

OK thank you for the continued replies. So to summarise the options to  heat up an object from about a metre away without large cumbersome ewuipment are:

IR, UV, normal type laser. All of which could be invisable to the naked eye.   Other than these are there any out of the box ideas? What about beta rays? Directing a stream of radiation. I welcome any out of the box idea here. Many thanks. 

[studiot]

Personally I favour a stream of warm air particles.
They are indistinguishable from ordinary air particles.

[Billy121]

12 minutes ago, studiot said:

Personally I favour a stream of warm air particles.
They are indistinguishable from ordinary air 

Thats an interesting idea. Thank you 

[swansont]

3 hours ago, Billy121 said:

Infra seems to show up on the most basic of cameras, just a normal iPhone show it very clearly. 

Again, that's not true. A camera sensor made of Si can only detect NIR (near infrared), and that's a common sensor that cameras use.

[Sensei]

On 4/11/2020 at 12:07 PM, Billy121 said:

Infra seems to show up on the most basic of cameras, just a normal iPhone show it very clearly. 

In this video author showed something exactly reverse:

 

Just checked. My Android smartphone is clearly showing whether my remote IR pilot is sending signal or not.

A 940 nm wavelength LED is typically used in remote controllers. [ref]

 

[swansont]

The front-facing camera may not have an IR filter even if the main camera does. It will let you see out to ~1.1 microns. Get a telecom laser at ~1.5 microns and it won’t work