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Complete the sentences given below with the missing words.

1) Three top inventions that changed the world are , and .

2) Penicillin is credited to scientist Alexander Fleming in .

3) Ernest Duchesne was a person who .

4) The father of electricity is .

5) Thomas Edison, Allessandro Volta, Andre-Marie Ampere and others contributed to our modern .

6) Most people believe that the light bulb was invented by . In fact, it was invented in by Humphry Davy, an English chemist.

7) Edison invented that burned for up to 40 hours.

8) It is said that Edison tried and failed over before finally perfecting the filament.

 

9. Discuss the questions:

1. How often do you watch TV, use your mobile phone?

2. Can you imagine your life without them?

3. What do you think was the most important invention of the last fifty years? Why?

4. What you think were the top 5 inventions of the last century. Give reasons for your opinion.

Unjumble the words to make sentences

know people physics dont how understand I. I think its a fascinating I more and wish understood subject really. our seems explain about Physics to everything world and our universe. to Its as though physics is the key unlocking all of our worlds mysteries. I really enjoyed studying physics at the beginning. It was interesting then. difficult But and then I it couldnt got understand the formulae. I have a lot of respect for physicists. They really to seem understand to lots be of able difficult things. Without them, we would still be living very basic lives. Physicists have sent people to the Moon. Their technology to modern led our has of research all. I always and fewer read to choosing are students fewer study physics. This is a shame.

Tell you groupmates what do you think about the quotation.

To invent, you need a good imagination and a pile of junk. (Thomas A. Edison)

LESSON FIVE

REFLACTION AND REFRACTION

Look at the definitions given below? Try to guess the words they define.

o a process in which light, other electromagnetic radiation, sound, particles, etc., are thrown back after impinging on a surface.

o the change in direction of a propagating wave, such as light or sound, in passing from one medium to another in which it has a different velocity.

Read the text about.

REFLACTION AND REFRACTION

1.____________________

Light rays usually travel in straight lines, but when they pass from one material to another they can be forcedto bend(change direction and continue on a new straight path). The bending is called refraction. It happens because light travels at different speeds in different materials. If light rays travel through air and enter a more densematerial, such as water, they slow downand bend into the more dense material. Light rays moving into a less dense material, such as from water to air, speed upand bend outwards.

Light rays bend or refract if they enter a glass block at an angle. When they pass from air into glass, they bend inwardsand slow down. They travel in a straight line through the glass at an angle to their originaldirection. As they pass out from the glass into air, they bend outwards and speed up again.

2.____________________

If you stand a strawin a glass of water, the top and the bottomof the straw no longer seem to fit together. This trick of the light is caused by refraction. Light bends outwards when it travels from water to air, so the eye sees the bottom of the straw (in the water) as deeper than the top of the straw (in the air).

3.____________________

On hot days, the surface of the Earth is warmer than the sky above it. This means that air close to the ground is generally much warmer than the air higher up. Hot air rising from the ground can bend and distortthe light rays passing through it. This gives a very hazy appearanceto objects, such as this giraffe, as they move on the horizon.

4.____________________ People who travel through hot deserts often think they can see water or trees on the ground ahead of them, when really there is nothing there. This trick of the light is called a mirage. Layersof warm and cold air bend or refract light rays coming from distant objects perhaps real trees over the horizon. Our eyes are fooled into thinking the light rays come from objects on the ground instead of from the sky.

5.____________________

Reflections are usually causedby shiny things, such as mirrors, that show a reversedimage of whatever is placed in front of them. The image seems to be as far behind the mirror as the object is in front of it. Not only mirrors make reflections, however. Most objects reflect some of the light that falls on them. In daytime we see familiar objects like grass, trees, and the sky only because they reflect light from the Sun into our eyes.

When light rays bounce off a completely smoothsurface, such as a stillpool of water, a mirror, or even something like a shop window, we are able to see a very clear reflection on the surface. Every ray of light is reflected perfectly from the surface and bounces back in a regular way. The reflected image is very clear and sharp.

6.____________________

A roughsurface, such as this rippling pond, causes light rays to bounce off it in many different directions. It may still be possible to make out an image on the surface, or, if it is very rough, the image is very broken up. Most objects reflect light in this irregular way. Although we can see them, we cannot see any images reflected in their surfaces.

7.____________________

A mirror is a very smooth, highly polishedpiece of metal or plastic that reflects virtuallyall the light that falls onto it. The reflection appears to be behind the mirror and may look bigger, smaller, or the same size as the thing it is reflecting, depending on the mirrors shape. We use mirrors when checking our appearance or driving. They also play an important part in telescopes, microscopes, cameras, and other optical (light-based) instruments.

A convexmirror curvesor bends outwards and makes an object look smaller and further away than it actually is. It makes light rays seem to come from a point behind the mirror, further from our eyes. Things look smaller, but convex mirrors are helpfulbecause they can show a widerpicture or field of view.

8.____________________

A concave mirror curves or bends inwards and makes an object look bigger and nearer than it actuallyis. It works by making light rays seem to come from a point in front of the mirror, which is closer to our eyes. Concave mirrors are important in such things as bicycle reflectors and reflecting telescopes.

A lot of men shave with the help of a concave mirror. Its curved surface makes the mans face seem closer to him than it really is. The reflected image he sees is magnifiedand he can easily see what he is doing. The mirrors drawbackis that less of the mans face fits into the mirror than in a flat mirror of the same size.

9.____________________

Drivers use mirrors to see traffic coming up behindthem. It is important for drivers to see as much of the road behind as they can, so wing mirrors and rear-view mirrors are convex. A drawback is that they make vehicles on the road behind look smaller and further away than they would in a flat mirror of the same size. Drivers must remember that the vehicles are nearer than they appear.

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