5338027
Description
Flashcards by Mr M Liddle, updated more than 1 year ago
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Created by Mr M Liddle
almost 8 years ago
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| Question | Answer |
| Explain the use of CAT scans. | X-rays are used to generate a 3D image on from lots of 2D images. |
| Explain the use of ultrasound. | Tissues and organs reflect ultrasound waves back and the time taken for them to return is used to measure their depth. This is used to create an image. |
| Describe the use of ultrasound. | Used to create images of unborn babies (foetal scanning) and of tendons, muscles joints and some internal organs. |
| Describe the use of endoscopes. | Used to look inside the body - commonly the reproductive and digestive systems, and the urinary and respiratory tracts. |
| Explain the use of endoscopes. | One bundle of fibre optics carries light using total internal reflection to the object and another returns an image for the doctor to view. |
| State the uses of non-ionising radiation in medicine. | Visible light used in endoscopes and laser eye surgery. Ultrasound used in foetal scanning. |
| State the uses on ionising radiation in medicine. | X-rays in CAT scans, x-rays and fluoroscopes. Gamma rays in radiotherapy and PET scanners. |
| Define the term myopia. | Short sightedness. |
| Define the term hyperopia. | Long sightedness. |
| Explain the use of laser eye surgery. | Laser eye surgery is used to treat myopia and hyperopia by changing the shape of the cornea using a laser. |
| Define the term radiation. | Any form of energy originating from a source, including both waves and particles. |
| State two factors that can affect the intensity of radiation. | The distance from a source and the medium through which it is travelling. |
| State the equation linking intensity, power of radiation and area. | Intensity = power of incident radiation / area I = P / A |
| Explain what causes the refraction of light. | The speed of a wave will change due to the density of the material it passes through. |
| Describe the relationship between the power of a lens and its shape. | The more curved the surface of a lens (thicker center) the greater its power. |
| State the main feature on the diagram of the eye. | The main features are the cornea, iris, pupil, lens, retina and ciliary muscle. |
| State the parts of the eye involved with focusing the light onto the retina. | The cornea and the lens are involved in focusing the light onto the retina. |
| State the near point and the far point of the average adult human eye. | The near point is 25 cm and the far point is at infinity. |
| Explain the symptoms and cause of short sight. | Someone with short-sightedness cannot focus properly on distant objects. This is caused by the eyeball being elongated, so that the distance between the lens and the retina is too great. |
| Explain the symptoms and cause of short sight. | Someone with long-sightedness cannot focus properly on near objects. This is because the lens focuses the sharpest image behind the retina. This defect is often age-related, and due to the lens becoming more crystalline. |
| Describe how short sight can be corrected. | It can be corrected by placing a concave lens in front of the eye. |
| Describe how long sight can be corrected. | It can be corrected by placing a convex lens in front of the eye. |
| Describe the law of reflection. | The angle of incidence = the angle of reflection. |
| Explain the cause of refraction. | Refraction occurs when light enters a more or less dense material causing it to change it's speed and direction. |
| State the equation for calculating critical angle. | sin c = 1 / n Where c is the critical angle and n is the refractive index. |
| Describe the term critical angle. | The critical angle is the angle of incidence for which the angle of refraction is 90 degrees. |
| Explain why total internal reflection occurs. | Total internal reflection occurs when waves pass form a dense to a less dense medium. If the angle of the incident ray is greater then the materials critical angle, then all the waves are reflected back into the medium. |
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