Task A – You must put the sentences below into the correct
order so that they form a flowing paragraph that describes
the discovery of Infrared by William Herschel
 Herschel performed more experiments on the rays he had discovered
beyond the red portion of the spectrum. He found that they could be
reflected and refracted in similar ways to visible light. He called this new
kind of light ‘calorific rays’, derived from the Latin word for ‘heat’. Today,
this form of light is known as infrared radiation. The word ‘infra’ comes from
the Latin word for ‘below’.
 He noticed that the temperature increased from the blue to the red end of
the visible spectrum. After noticing this pattern, Herschel decided to
measure the temperature just beyond the red portion of the spectrum in a
region that did not appear to have any sunlight falling on it.
 He thought that the colours themselves might be of different temperatures
and came up with an experiment to investigate his hypothesis.
 Herschel passed sunlight through a glass prism to split the light into the
spectrum of colours, and then measured the temperature of a thermometer
lit by each colour in turn.
 An astronomer named Sir Frederick William Herschel (1738-1822), famous
for his discovery of the planet Uranus in 1781, made another important
contribution to science in the year 1800. In his astronomical work, Herschel
noticed that when he used filters of different colours to observe sunlight, the
filters seemed to let through different amounts of heat.
 To his surprise, he found that this region had the highest temperature of all.
He realised that there must be another type of light beyond the red, which
we cannot see. (He probably could not have been expected to discover
ultraviolet light beyond the blue end of his spectrum, as his glass prism
would have absorbed most of the ultraviolet light.)
 Herschel’s experiment is important because it was the first time someone
showed that there are types of light we cannot see with our eyes. As we
now know, there are many other types of radiation that we cannot see, and
the visible colours are only a small part of the whole electromagnetic
spectrum.
Task B – You must read the paragraph below and answer the
questions below.
I was very interested to hear that William
Hershel had discovered heat beyond the red
wavelength of the spectrum. I was intrigued
enough to start investigating ‘invisible light’
and looked for a possible cooling effect at the
violet end of the light spectrum.
I had been doing some experiments with
Silver Chloride (which blackens in sunlight)
and decided to test it with different colours of
the spectrum. There was no discolouration
with red light but it massively increased
towards the violet, hmmmm……what was
going on?
I then put some Silver Chloride in an area just
beyond the violet part of the spectrum i.e.
where it was dark! To my amazement the
Silver Chloride went completely black well
beyond the violet edge of the visible
spectrum. Wow! I was amazed, I called this
new form of light ‘Chemical Rays’ catchy eh?
1. What was the hypothesis
that Ritter had about the
violet spectrum?
2. What chemical was used
by Ritter that is sensitive
to sunlight?
3. What part of the
spectrum is this chemical
more sensitive to?
4. If Ultra violet is not visible
to the naked eye, then
how did Ritter know he
had discovered it?
Task C
You must use the information to write a story board (3
pictures) for each of the discoveries.