Flashcards
Cooking and Communicating using Waves
Cards in this deck (15)
- 1What are the two ways of cooking?By using infrared radiation or microwaves.
- 2Give some examples of cooking with infrared.Examples:
Toaster,
Hob,
Or an oven. - 3All objects give out infrared radiation, but some give out more what are these?Hotter objects emit more infrared than cooler ones.
Black objects emit more infrared than pale ones at the same temperature.
Rougher or dull surfaces emit more infrared than shiny ones at the same temperature. - 4Food in an oven gets hot because it absorbs the infrared that the oven is emitting, but which type of object absorbs more than others?A black object absorbs infrared better than a pale one so it gets hotter more easily.
A shiny object reflects infrared so it cannot absorb it and does not get hot as easily. - 5How does infrared cook food?When an object absorbs infrared, the energy from the electromagnetic wave is absorbed by the particles in the surface of the object and so their kinetic energy increases (they vibrate more). This means that the temperature of the object will increase. Some surface particles become so hot that they get damaged and become brown (burnt).
The hotter surface particles then transfer energy to particles in the centre by conduction so the whole thing cooks through. - 6What are microwaves?They are electromagnetic waves.
- 7What reflects microwaves and what can they penetrate through, how does this mean in the cooking process?Shiny metal surfaces reflect microwaves, which is why you should not put metal objects into a microwave oven.
Microwaves can penetrate through glass or plastic, so food in containers made from these materials can cook easily. - 8How do microwaves cook food?The waves penetrate about 1cm into food and The water and fat molecules in the outer layers of food absorb the microwaves efficiently and the energy increases their kinetic energy, making the material hot. The food should be stirred to enable heat to be spread through the food.
- 9Why are microwaves faster at cooking food then infrared, and why are they more dangerous?Because microwaves have longer wavelengths than infrared, they are absorbed by water and fat more easily than infrared. This means they cook food more quickly and are more able to cause burns on body tissue.
- 10Microwaves in communication, what do they do?They can transmit information over large distances that are in line of sight, which means that the transmitters and receiver must have no obstacles between them. Some areas are not in line of sight so they have poor signals, which is why your mobile phone may cut out or fail to get a connection.
- 11Why could microwaves sometimes have poor signal?This could be due to:
A large obstacle such as a building or a mountain.
The signal being affected by the weather or a large area of water.
The curvature of the Earth.
The signal getting weaker as it travels further. - 12How is it possible to try and reduce signal loss?By putting transmitters and receivers close together and by positioning them on high ground so that buildings, hills etc. do not get in the way and so that the curvature of the Earth has less effect.
- 13What can you not rely on to help reduce signal loss?It is not possible to rely on diffraction of microwaves around buildings, hills etc. because their wavelength is not large enough. It is also impossible to do anything to stop interference between signals.
- 14What is the health concern with using mobile phones?Mobile phones use microwave signals but they are not the same wavelength as those used in microwave cookers.
There is public concern about children using mobile phones because their skulls are thinner and people think their brains may get damaged by the microwaves. There is also concern about possible dangers to adult users and people who live near transmission masts, even though there is no evidence of any effect on people when thorough tests have been carried out. - 15What do the studies into the effect sof mobile phones show?There have been many studies, and almost all show that there is adverse effect on people who use mobile phones or live near phone masts. Some studies show a link between frequent phone use and brain tumours but they do not show that the microwaves from phones or phone masts cause these tumours or any effect on health.
All the studies have been published this makes it possible to check all the results and compare the conclusions.
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- GCSE Physics (P1) Flashcards on Cooking and Communicating using Waves, created by Rebecca Smith on 02/11/2016.
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- Rebecca Smith
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