OpticsEdexcel GCSE Physics: Flashcards

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State the law of reflection.

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State the law of reflection.: The angle of incidence equals the angle of reflection, both measured from the normal.
What causes refraction?: A change in the speed of a wave as it passes from one substance into another with a different density.
When does total internal reflection occur?: When light travelling in a denser substance hits a boundary at an angle greater than the critical angle.
What is the critical angle?: The angle of incidence above which total internal reflection occurs.
What is the difference between specular and diffuse reflection?: Specular reflection is from a smooth surface (light reflects in one direction); diffuse reflection is from a rough surface (light scatters in many directions).
Why does a red object appear red in white light?: It absorbs all other colours of light and reflects red light to our eyes.
How does a colour filter work?: It transmits only certain wavelengths (colours) of light and absorbs the rest.
What determines the power of a lens?: Its focal length and shape — a more curved lens with a shorter focal length has a higher power.
What type of image does a diverging lens always form?: A virtual, upright, diminished image.
What is a real image?: An image formed where light rays actually meet, which can be projected onto a screen.
What is a virtual image?: An image formed where light rays appear to come from but do not actually meet, which cannot be projected onto a screen.
In the core practical investigating refraction, what is measured at the point light enters the glass block?: The angle of incidence and the angle of refraction, both from the normal.
Does light bend towards or away from the normal when entering a denser substance (e.g. glass)?: Towards the normal.