Alice, Daisy, Eliza (10) asked “What chemical makes objects glow in the dark?”

Thanks team. I think we will start by looking at the meaning of the words that end in the term ‘escence’.

Fluorescence is the the almost instantaneous emission of light by a chemical that has absorbed light or some other form of energy and  then re-emits it.
Chemiluminescence is used to describe the production of light from a chemical reaction.
Bioluminescence is used to describe the production of light from a living organism. It is a form of chemiluminescence as it is chemicals within the organism’s body that produce the light.
Incandescence is the emission of light from a hot body. A heated piece of iron will glow.
Phosphorescence is the slow emission of light from a compound that has absorbed some energy, in some form…might be radioactive energy.

Note all of them involve , at one time gaining energy and then re-emitting it or chemicals moving from one state to another where the final state is of lower energy.(If you want to find out a little bit more on energy go to this Science Master Special)

If you have access to a low intensity UV torch ( check with an adult) you can look at at the compound Quinine for an example of fluorescence. Quinine is a compound in Tonic Water. In a dark room shine the torch (a UV torch produces BLACK light) on the bottle of tonic water and watch what happens. You can then make some ice lollies using the tonic water and again see if they are fluorescent.

Thanks for the question. If you want to make a comment feel free to do so in the box below…or maybe…you have a further question?

(Revised 13/9/17 – added energy link)

Ava (7) asks “Why do mirrors change words ?”


Ava, can you see how the image of the dog in the mirror is different from the dog. Look at the dogs raised ear. What side of the head is it on? NOW imagine you are the dog in the mirror, what side of the head is the raised ear on.

Try this, look in a mirror and point your right finger at the mirror. Now try to put yourself in the position of you in the mirror and what side of you is your finger. Is it your right finger or left finger, in the mirror???  Wow. The mirror has inverted your image (the dictionary says inverted means  – put upside down or in the opposite position.)

Now try a mirror with some words. Try it with this word  Mirror Me. Write it on a piece of card or paper and look at it in a mirror. What does it look like …..is it like this?

Think about what you are seeing. Why can you see the image in the mirror? Think about reflection? This is a very difficult area of understanding BUT you can have a lot of fun with it.

Updated 12/6/17

“I know I can see myself in a mirror but why cannot I see myself in other things?” asks Isabella (8)

Many thanks team. I have some ideas about investigations that you could do at home. People say that light travels in straight lines. How can we test this idea. Firstly we need a source of light. How about a torch. 

Now we know that a torch sends out light in all directions but how do we know if it is travelling in a straight line? Think……..

Now lets ‘capture a little bit of the light from the torch. Let’s use a piece of card with a hole in it and see if we can make the light from the torch go through the hole.

Now what do we have to do to show that, the little beam of light coming through the hole is travelling in a straight line?
Supposing we had another piece of card with a hole in it in exactly the same spot do you think you could arrange it so that the little beam of light goes through the hole in the new piece of card?

Do the same for a third piece of card arranging it so the little beam goes through it’s hole. Now draw a line between the torch and the third hole. What do you notice?

Now lets quickly look at your question about not seeing reflections in materials that are not mirrors.

Reflections are wonderful things and they happen, or do not happen because light travels in straight lines. A reflection occurs when a beam of light bounces off a surface. You could set up your torch and card above to make a reflection, using a mirror or something flat and shiny.

Now do the same for a different type of surface.try it with a piece of material. What happens? Try with all sorts of flat surfaces – shiny metal (use flat aluminum foil and then crinkle it), cardboard, paper, plastic, water, leather……..
What do you notice? Maybe reflection requires a flat shiny surface? Think about the results.

“Is a shadow a reflection?” asks Jack (7)

Thank you team. Some excellent observations. You noticed that the shadow had no detail on it, no colour, no lines, no images of seeds in the fruit. It was just black. On a dark night, under street lights look at your shadow. Other than your shape what detail does it have? It changes now and again, but why?

Now the reflection? If you look into a mirror what do you see? Is it like your shadow? How different is it?

Look at the two images of the fruit. The first image of the the fruit is the ‘real’ image. What about the image just below it (on the shiny surface)? Is it the real image? How did it get there?

Think about this – where did it come from? Now think about your image in a mirror, where did that come from?

You can create you own image of a reflection and a shadow. Get a mirror and a small screen. Put the object on the mirror and the screen behind it and use a torch to shine on the object.

Jack, this a great question. Lot’s to think about. Do you want to ask another question? Then click on the Reply button below.

 

Beatriz (7) asks “What happens to the the light at night?”

How do we tackle this question Beatriz? Lets tackle it by looking at light being used.

Let us see if we can make light move around a table. For this experiment you will need 3 plastic mirrors some plasticine and a torch. Light can be ‘bounced off’ an object so can it be bounced off mirrors?

So your task is to bounce the light from the torch around the four sides of the table. Think about what you did to make it happen.

Also let us look at shadows. Collect a variety of objects, a torch and a screen (maybe mounted in some way). Shine the torch at the object, what do you see on the screen.

Why do you think the shadow is formed? Can you change the shape of the shadow? Can you get more than one shadow?

Any reader can ask another question or leave a Comment in the Leave a Reply box below

How do we know what organelles inside a cell looks like? – asks Anne (7th Grade)

How do we know what organelles inside a cell looks like? Anne, a fascinating questions. I have to be honest I have no idea what an organelle is (I am traditionally what might be called a physical scientist) – I know a lot about physics and chemistry but very little about biology and botany. I do have a team who can set me on the trail of answering you question so here goes…..over to you team.

organlles

Thanks team. Some other questions ‘bounce’ around my mind. Why can’t light bounce of the organelles? I then realised that it is thought that light is in fact particulate  in nature. Scientists think that light might consist of particles – called photons. These photons are basically to big to bounce of such a small particle as an organelle. They could bounce off but when you look at them after the bounce they will not be able tell you anything about the thing they bounced off.

As my team suggest electrons are much smaller than photons, so when they bounce of the organelle they will reflect what the organelle at that point looks like. To do this scientists use special microscopes called electron microscopes  that instead of firing light (photons) at the thing they want to look at fire electrons and look at how the electrons have changed after they have bounced of the thing you are looking at.

Anne, hope this makes sense. Thanks for the question. Unsure about what I have said then you can ask another question.

Soham (10) ask “Why is the sky blue”

Soham, I have tried with my friends to answer this question previously. Have a look at my a previous answer.

Think about it and if there is something that you are unsure of ask another question. Sometimes other questions help. They  help all of us to understand some of the strange aspects of our lives.

Soham(10) asks – “Why do Chameleons change their colour and how ?”

chameleon

Thanks team, some good answers. On most occasions it is suggested that a Chameleon changes colour for defensive purposes.  It seems that they can do this by changing the tension in their skin. Not something that we can do very easily. For the Chameleon, part of the skin is a compound that can be stretched and it is this compound that changes the light colours that are absorbed by the skin and those that are reflected. Thus the colour change.

Reflection of light of things depends on the material and the light that is falling on it. Suppose green light was shone on a red object in a dark room. Would you see it? Sometimes you can also notice that changing the temperature of a material changes the way it reflects light. Running a hot iron over a red material changes the ‘redness’ of the material because of the effect of the heat on the compound that the red dye is made of. Some experiments that you might try (with the help of an adult).

Why is the sky blue in the day and black in the night? asks Lamar (12)

Lamar – a brilliant question. I will ask my friends to think about it.

blue-sky

Lamar. I hope that you have had the opportunity of passing ‘white light’ through a prism and see the fantastic ‘spectrum’ of coloured light that results. If not then try ‘creating’ white light by using torches and  coloured cellophane (blue, red, green) on each torch and shining them at a white piece of cardboard. Let me know what happens.

Things then get a little difficult. You have to think of the Sun’s white light reaching the atmosphere of the Earth. The two major components of the atmosphere are nitrogen and oxygen. The structure of the molecules of these two components makes them very receptive to the blue part of the white light from the Sun. The air molecules absorb this blue part and then re-emit it in all directions. This is a process called ‘scattering’. Thus the blue sky. The rest of the (white minus some blue) sunlight passes onwards.

At night the Sun is shining on another part of the Earth, so no white light is falling on your part of the Earth. No light ….blackness.

Lamar . An interesting question, a complex answer. Feel free to ask another question.

Balqisa asks “Do adults have have a different eye sight to kids”

An excellent question.

Balqisa asked a question on how does the eye work and what is it made of. I have tried to make the image below to show you how it works. The eye is complex and is made of lots of different things. For example it has it’s own sets of muscles which can stretch the lens and allow your eye to focus. It is filled with a special fluid that allows light to pass through it and gives the whole eyeball a very ‘squashy’ feeling. It is also connected to the brain by something which we call the optic nerve.

The eye
How is the adult eye different from this?. Not very much, BUT the older person’s eye does change. Early into adulthood the liquid in the lens begins to solidify, this causes a lack of focus on objects close to you. As we get even older the muscles that control pupil size get weaker, these control our reaction to light, so glare is to be avoided. We also have less tears and more importantly our peripheral vision decreases.
Thank you Balqisa for making me feel old.