Science

• Light is part of the electromagnetic spectrum.
• Virtual images are formed when diverging rays are traced back to where they appear to cross.
• We use three rays to work out where images form.

   

  The first ray travels parallel to the principal axis and passes through the focus on the other side of the lens.
• The second ray goes from the object straight through the center of the lens.
• The third ray travels through the focus closest to the object and then travels parallel to the principal axis on the other side of the lens.

   
• If an object is placed closer than the focal length (F) of the lens, then the image will be virtual, erect, and smaller than the object.
• If the object is placed closer than the focal length, the image will form behind the lens. If it’s further away, the image will form in front of the lens.
• When white light passes through a glass prism, it splits into seven colours, forming a spectrum.
• Every colour in the spectrum has its own wavelength and corresponding frequencies and energies.
• As light passes from one transparent substance to another at an angle, it refracts, with each colour refracting by a slightly different amount, resulting in different angles of refraction; red light refracts the least and violet light refracts the most, with the other colours spread out in between.
• Objects appear to have specific colours because they reflect certain wavelengths of light while absorbing others; for example, a blue object reflects blue light and absorbs other colours.
• Black objects absorb most light, causing them to appear black and to heat up more in sunlight compared to white objects, which reflect most light and remain cooler.
• We see colour because the wavelength of that colour is being reflected and all other wavelengths of the spectrum are being absorbed.
• When light passes through a filter, the filter lets that coloured light pass through it and it absorbs the other colours.
• Electromagnetic radiation, or EMR, is travelling energy that displays properties of both waves and particles.
• If you stand between the center of curvature and the focal point for a concave mirror your image will be inverted, enlarged, and real.
• If you stand at the center of curvature of a concave mirror, your image will be the same size, inverted and real.
• If you stand in front of a convex mirror, your image will always be upright, diminished, and virtual.
• There will be no image if you stand directly on the focal point of the mirror.
• If you stand closer to a convex mirror than its focal point, your image will be upright, virtual and enlarged.
• The electromagnetic spectrum is made up of several different types of waves. These waves have different amounts of energy, starting from low to high.
• All electromagnetic waves travel through air at 300 000 000 metres per second.
• Unlike sound waves and water waves, electromagnetic waves can travel through a vacuum.
• Radio waves include the low-energy waves that are used to communicate through radio and tv, they also include radar and microwaves (to cook food).
• Microwaves have shorter wavelengths than radio waves, and they range from less than 1 metre down to 1 millimeter.
• Infra-red radiation, invisible to the human eye, is emitted by all objects and is sensed as heat.
• Visible light represents only a very small part of the electromagnetic spectrum.
• Ultraviolet radiation is needed by humans to help the body produce vitamin D; however, too much causes sunburn, damages skin cells and cancer. In medicine, ultraviolet light is used to help kill bacteria and viruses and to sterilize equipment. It is also useful to study atoms far away in space.
• X-rays have enough energy to pass through human flesh. They can be used to kill cancer cells, find weaknesses in metals and analyse the structure of complex chemicals.
• Some parts of the human body absorb more of the energy of X-rays than others. For example, bones absorb more X-ray energy than the softer tissue around them. This makes X-rays useful for obtaining images of bones and teeth.
• Gamma rays have even more energy than X-rays and can cause serious damage to living cells.
• Gamma rays can be used to kill cancer cells and find weaknesses in metals.
• Gamma rays are produced when energy is lost from the nucleus of an atom. This can happen during the radioactive decay of nuclei or as a result of nuclear reactions.
• the order of electromagnetic waves goes Radio, microwave, infrared, visible, ultraviolet, X-rays, gamma rays
• Radio waves have the longest wavelengths (1 mm - 100 km), the lowest frequency and the least energy of all the forms of EMR.
• Microwaves have long wavelengths (11 mmmm to 1010 cmcm), low frequency and low energy.

   

  These properties makes microwaves perfect for transmitting information over long distances
• Infrared falls along the electromagnetic spectrum between microwaves and visible light.

   

  Infrared has longer wavelengths (700700 nm−1nm−1 mmmm), lower frequencies and lower energy than visible light.

   

  Infrared rays travel through the atmosphere and their energy is felt as heat.
• Visible light makes up only a small section of the EMR spectrum.

   

  It includes all wavelengths between 400400 and 700700 nmnm.

   

  Colours are produced by light waves of different frequencies and wavelengths. White light is a combination of the entire colour spectrum. Objects around us are coloured differently depending on the wavelengths that they absorb and reflect.

   

  Red has the longest wavelength and the lowest frequency of all the colours. Violet has the shortest wavelength and the highest frequency of all the colours.
• Ultraviolet radiation, also known as UV, falls along the electromagnetic spectrum between visible light and x-rays.

   

  It is produced by very hot objects like the Sun or solariums. UV has short wavelengths, ranging between 10−40010−400 nmnm, high frequencies and high energy.
• X-rays come next on the EMR spectrum, sitting between UV and gamma rays.

   

  X-rays have a short wavelength, ranging from 0.01 nm0.01 nm to 1010 nmnm. They also have a high frequency and high energy level.