EVS week 4 & 5 - optics

how do convex lens refract light?

• they refract parallel rays of light inwards to a single point i.e. principle focus

• they bulge in the centre

do convex lenses converge or diverge rays?

• they converge light rays (bring to a single point)

how do concave lenses refract light?

• they refract parallel rays of light outwards/disperse the light

how to figure out the direction that light rays on a concave lens will be refracted in?

• first, draw virtual lines from the lenses principle focus to where the rays hit the lens

• then, if we continue these lines, we will see where the real rays will go

where is the principle focus (focal point) of the lens?

• it is found on both sides of the lens

• they will be equal distances from the centre

what is the focal length?

• it is the distance between the principle focus and the very centre of the lens

where does the focal point always sit?

• it will always sit on the axis (a line passing through the middle of the lens)

does focal length have an effect on the power of the lens?

• yes, it has an effect on the lens’ power

• the more shorter the focal length, the stronger the power of the lens

  • i.e. the lens will refract light more strongly

how can we make a lens more powerful?

• we can either make the lens more curved

or

• we can use a different material that naturally refracts light more strongly

what makes an image real?

• an image is real when the light rays actually come together to form an image

what makes an image virtual?

• a virtual image is formed when the light rays don’t come together where the image appears to be

in a diverging/concave lens, if you put an object in front of the focal point, how will the image appear?

• the image will be smaller and virtual

in a converging/convex lens, if the object is placed to the left of the focal point, how will the image appear?

• the image will be small, inverted and real

if an object is placed to the right of the focal point with a converging/convex lens, how will the image appear?

• the image will be virtual, enlarged and upright