2. Lenses 3.0 / 5 based on 1 rating ? PhysicsLight and OpticsGCSEAQA Created by: Vicky FursdonCreated on: 22-02-13 10:54 Define refraction: When a wave changes speed (and therefore direction) when entering into a different medium 1 of 16 What happens to the refractive angle if the wave slows down? It bends towards the normal 2 of 16 Define the refractive index: the ration of the speed of light in a vacuum to the speed of light in the new medium 3 of 16 How do you find the refractive index? Sin angle of incident/ Sin angle of refraction 4 of 16 What are converging lens? convex lens - the principal focus is where the rays meet on the axis if they have hit the lens parallel 5 of 16 What is a diverging lens? Concave lens - the principal focus is where the rays hitting the lens parallel look like they have come from 6 of 16 What is a virtual image? When the rays are diverging so the light from the object makes it appear in a different place 7 of 16 What is a real image? The light from the object is projected onto a screen 8 of 16 What will the image be if the object is at 2F? It will be real, inverted, same size and at 2F on the other-side of the lens 9 of 16 What will the image be if the object is between F and 2F? It will be real, inverted, bigger and beyond the 2F on the other side of the lens 10 of 16 What will the image be if the object is between F and the lens? It will be virtual, the right way up, bigger and on the same side of the lens 11 of 16 How near the focal length does the image have be to be magnified? It must be nearer to the lens than the principal focus 12 of 16 How can you work out the magnification of a lens? Magnification = image height/ object height 13 of 16 What is the formula for the power of a lens? Power (D) = 1/Focal length (M) 14 of 16 Is the power of a converging lens positive or negative? Positive (diverging Len's power is negative) 15 of 16 What 2 factors affect the focal length? Refractive index and curvature 16 of 16
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