Question

If light is part of a spectrum why can we only see light and not the other parts of the spectrum? If we can only see light why can we infrared filters in a camera? And will we we ever evolve into creatures that can see other forms of energy too?

Answer 1

Go through the following questions, it will solve all the doubts you have

Hey, why can't we see past the visible spectrum?

Because our eyes have evolved to only look at that part of the spectrum.

Okay, but why have we evolved to see only a thin slice of the spectrum? Why not the whole spectrum?

Seeing and perceiving the whole spectrum is computationally expensive. Our brains would be overwhelmed with all that data. And, we're doing just fine with our present capabilities. There's just no great need to see the whole spectrum.

So it's wasteful to see the whole spectrum. But why do we have to see only that specific part of the spectrum? Why not some other part of the spectrum?

We see what we see because that's the most relevant for us. Bees and butterflies can see well into the ultraviolet spectrum, because it helps them to easily identify nectar in the flowers. We don't see UV because it's just not relevant.

Yeah, but why has this tiny part of the spectrum become so relevant for us?

It's relevant to us because the light we use to see things is mainly sunlight, and the majority of sun's light happens to fall in that part of the spectrum (400 to 700 nano-meters in wavelength). Have a look at this picture:

Nocturnal animals like snakes for example, need to move around at night, when the sun's light is scarce. So, they have evolved to look at the infra red part of the spectrum, in other words, they can sense the body heat (thermal energy) of their prey.

That's interesting! So, we have evolved to see whatever light is thrown at us. But why does the sun give out so much light in that wavelength?

It's because of the temperature of the sun. The radiation that a star gives out depends on it's temperature. Look at that green curve in the previous graph. Sun is akin to a black body at a temperature of 5777 Kelvin.

And, why is the sun at that temperature?

The sun was not always at that temperature. It used to be hotter, but it's cooling down now. It was hot because stars are born out of nuclear fusion of giant clouds of dust compressed under the pressure of their own gravity, and nuclear fusion gives out the heat which makes the stars hot.

This gives answer to your doubts, our eyes won't evolve to see IR because in the current scenario it is not required. If it is necessary for our existence we will definitely evolve.

We can see Infrared through cameras that's because camers receives IR and process the data to visible light that we can see