This document provides an overview of light and the electromagnetic spectrum through a series of images and captions. It discusses how light travels from the sun, the different types of electromagnetic waves including visible light, infrared, ultraviolet, x-rays and gamma rays. It also summarizes how artists use light effects, how humans and other animals perceive light, and examples of bioluminescence in nature. The document aims to educate about light and its properties and interactions.
Forensic Biology & Its biological significance.pdf
International light day scrolling presentation
1. “You don’t see light until it shines on something”
- Oliver Postgate, The Clangers, 1971
2. Artists like John Grimshaw (1836-1893) used the strange effects
of light, clouds and atmosphere in his paintings.
3. The light we see from the sun took 8 minutes 20 seconds to
reach the Earth.
So we see the Sun as it was 8 minutes 20 seconds ago.
What were you doing 8 minutes 20 seconds ago?
From: Wlpapers.com
4. The sun’s light you see
now was made in the
core of the Sun
millions of years ago!
It starts off as X-rays,
which bump into the
Sun’s atoms losing
energy until they reach
the surface.
Image from “Science Picture/Corbis”
5. Darkness is often associated with sadness or
depression in books and plays:
“Away from light steals home my heavy son,
And private in his chamber pens himself,
Shuts up his windows, locks fair daylight out,
And makes himself an artificial night.”
- Montague, Romeo’s father, in Act 1 Scene 1 of “Romeo
and Juliet”, talking about Romeo, who is depressed.
6. Gamma rays, X-rays, ultraviolet waves, visible light, infrared,
microwaves and radio waves are all the same thing, but with
different amounts of energy.
They are all waves made of tiny packets of energy called
“photons”.
Image from “Ask a Scientist”.
7. This is what the Crab Nebula looks like at different wavelengths.
The Crab Nebula is the remains of a star that exploded nearly 1000
years ago. It was so bright, people in America and China saw it by
daytime.
22. Photo: Alice Sheppard (from Lewisham station)
Crepescular rays
are stripes of
shadows cast by
clouds and air with
particulates lit up
by the sun.
23. Birds and bees can see in ultraviolet light.
Flowers look like targets to them!
Photos: Andrew Davidhaz, Rochester Institute of Technology
24. Snakes have infra-red sensing membranes near their eyes.
So they can’t “see” in infra-red, but they can sense, and they
have bad eyesight. Perhaps this is what a mouse looks like to
them ….
Pictures: Quora; Encyclopedia Britannica
25. Painting: “Open Window on a
Garden” by Konstantin Samov,
1934.
Notice how the artist uses light
and shadows to make objects
clearer and brighter.
26. Blue objects reflect blue light, red objects reflect red light.
In late evening or early morning, try turning the lights off. Things will appear
blue. Blue objects (a pair of jeans?) will look pale. Red objects (a KitKat
wrapper?) will look dark.
Image: design.tutsplus.com
27. Plants absorb red and blue light, but reflect green light.
Scientists studying plants at “night” shine green light on them to see.
The plants reflect that light and continue to behave as it it’s night.
Image: hackerfarm.jp
28. Lightning creates light because the electric current heats the air it passes
through: it reaches 27,000°C, 6x hotter than the surface of the Sun!
Image: Stephen Cheatley
29. A light year is a unit of distance, not time.
It’s the distance light travels in 1 year.
It’s 5,878,625,373,184 miles!
The nearest star to the Sun is called Proxima Centauri. It’s so
small we can’t easily see it. It’s 4.3 light years away.
30. The constellations look
flat, but the stars in them
are at different distances
away from us.
If you were on
Betelgeuse, you’d see
the Earth as it was in the
time of Shakespeare.
Betelgeuse looks orange,
because it’s a red giant. It
will explode as a
supernova one day.
Maybe in your lifetime?
31. A meteor (“shooting star”) gives off light because it moves
so fast, it compresses the air in front of it, which heats up.
It’s not because of friction!
Photo: NASA/JPL
33. The aurora is caused by energetic particles from the solar wind
striking particles from the Earth’s atmosphere. The energy is
released as green, red or purple light.
Image: Tommy Richardson.
34. The aurora also appears on Jupiter and Saturn.
Magnetic fields direct the energetic particles from the solar
wind towards the poles. That’s why the aurora appears there.
35. The surrealist artist Rene Magritte used light and dark to confuse.
Is it night or day in this picture?
36. Deep sea creatures use
light to communicate
with each other and find
food.
Producing your own
light is called
bioluminescence.
Bioluminescence has
evolved about 40 times
independently!
Image: National Oceanic
and Atmospheric
Administration (NOAA)
37. Photo by John Tyler
Female glow worms use
bioluminescence to find a
mate.
Light pollution makes it
harder for male glow worms
to find the female glow
worms.
You can often see glow
worms in the country, waiting
for mates on grass or
branches.
38. “We can easily forgive a child who is
afraid of the dark; the real tragedy of
life is when men are afraid of the light”.
This means it’s OK to be scared when you are
young, but it isn’t good to be scared to learn
new things as you grow up.
Light is associated with knowledge.
This quote is often attributed to Plato, but there
is no record of him saying or writing that.
Nobody really knows who said it first.
Plato statue from Wikipedia
39. If you shone a light beam
with a torch you could never
catch up with the light.
Light is the fastest thing in
the universe. Nothing can
catch up with it.
Image: Wikipedia volunteer “Lumenbuddha”
40. Dark can be a good thing. It helps us sleep, and nocturnal (night-time) animals rely on
it. And we can’t see stars without the dark!
“Earth Hour” and the “Campaign for Dark Skies” encourage people to switch off their
light or use less invasive lighting so we and many animals can be healthier.
Image: “Visit Coll” (Coll is an island west of Scotland).
41. Shadows on the Moon are
really dark because there’s no
air on the Moon.
Air diffuses light, meaning it
sends it in lots of different
directions. That’s why
shadows are so faint on a
cloudy day.
You can tell there is no air on
the moon because the edges
aren’t blurry, like the horizon
on Earth.Picture: Apollo archives.
42. Retroreflectors reflect light back to its source so will
reflect at a lot of angles. You will see some at the
demonstration tables.
Cats’ eyes are natural retroreflectors. This helps cats see
at night.
Bicycles are also equipped with retroreflectors. They
catch light from nearby car headlights, even if the car
isn’t right behind the bicycle.
All images: Wikipedia
entry on retroreflectors.
43. Picture: NASA Apollo archives.
There are retroreflectors on
the Moon.
From Earth we shine lights on
the moon. The light bounces
off the retroreflectors. We time
how long it takes to get back.
This tells us how far away the
Moon is.
This is how we know the Moon
moves away from the Earth at
4cm/year.
44. In a solar eclipse the Moon goes in front of the Sun (from our
point of view).
This way we see the sun’s light shining on its atmosphere. It’s
usually too bright to see this.
Image: M. Druckmüller.
45. Ultraviolet light
Suncream works because it
contains tiny, shiny particles
(e.g. zinc oxide) which
“scatter” the ultraviolet light,
sending it in lots of directions
away from the skin.
Suncream may also contain
nanoparticles (tiny particles,
often of carbon) which absorb
the ultraviolet light.
46. Humans have 3 types of cones - to see red, green and blue.
Mantis shrimp have 16 types of cones for different colours!
They can see linear and circular polarisation, which is special
shapes of light waves. Sunglasses use polarisation to filter out
some sunlight.
Image: Nina Meinzer
47. Although sharks are very
likely colour blind, they
can sense (other)
electromagnetic fields
over long distances. This
helps them find wounded
prey animals.
Image: Wikipedia Commons
48. This presentation was made for the
International Day of Light event at
UCL, 15th May 2018
By:
Alice Sheppard, UCL Extreme
Citizen Science and “Doing It
Together Science”
With:
Nina Meinzer, Nature
Communications
Notas do Editor
I haven’t explained the causes of bioluminescence here as they seem VERY complicated. Kids tend not to learn about enzymes until they’re in GCSEs. I can add another slide going into this ….
