GRADE 9 Integrated Science – Curved mirrors Quiz

A curved mirror is a reflective surface that is not flat; it is usually part of a spherical or cylindrical surface which causes light rays to converge or diverge.

For a concave mirror, rays parallel to the principal axis reflect and meet at the focal point in front of the mirror.

A spherical mirror is part of a sphere; the centre of curvature is the centre of that sphere.

The principal axis is the straight line through the mirror's vertex and the centre of curvature; it is the main reference line for ray diagrams.

Parallel rays to the principal axis reflect from a concave mirror and converge at the focal point in front of the mirror.

A convex mirror causes incoming parallel rays to reflect and diverge; the extensions of these reflected rays meet at a virtual focal point behind the mirror.

When the object is beyond the centre of curvature, a concave mirror produces a real image that is inverted and reduced in size.

If the object is at the centre of curvature, the image is formed at the same position (centre of curvature), is inverted and equal in size to the object.

An object at the focal point produces reflected rays that are parallel; they do not meet to form a finite image, so the image is formed at infinity.

When the object is between the focal point and a concave mirror, the mirror produces a virtual, upright and magnified image.

Convex mirrors always form images that are virtual, upright and smaller (reduced) than the object, regardless of object distance.

When the face is held within the focal length of a concave mirror, a magnified, upright virtual image is produced, which helps with close work like shaving or make-up.

Convex mirrors diverge rays and produce smaller upright images, allowing drivers to see a wider area behind and to the side of the vehicle.

For a spherical mirror, the focal point is halfway between the vertex and the centre of curvature, so f = R/2.

Using 1/v = 1/f - 1/u = 1/10 - 1/30 = 1/15, so v = 15 cm in front of the mirror (real image).

With v = 15 cm and u = 30 cm, magnification m = v/u = 15/30 = 0.5. A positive or absolute value less than 1 indicates a reduced image; for a real image by a concave mirror it is inverted.

One principal ray is parallel to the axis and after reflection passes through the focal point; other principal rays include ray through centre of curvature (reflects back along itself).

In a convex mirror, a ray that appears to be directed toward the virtual focal point (behind the mirror) will reflect and emerge parallel to the principal axis.

Placing a light source at the focal point of a concave mirror makes the reflected rays parallel, producing a directed beam useful in torches and headlights.

Convex mirrors give a wide angle of view and produce upright, reduced images, allowing a shop attendant to see a larger area for security.

Convex mirrors diverge rays so the image is always virtual (behind the mirror), upright and reduced in size.

Distant (effectively parallel) rays reflect and meet at the focal point, so very far objects are imaged at the focal point of a concave mirror.

When the object is located at the centre of curvature of a concave mirror, the image formed is the same size as the object (but inverted) and is located at the centre of curvature.

At close distances (object inside the focal length), a concave mirror produces a virtual, upright and magnified image useful for detailed examination.

Reflecting telescopes use large concave mirrors to collect parallel light from distant objects and focus it to form an image.

Convex mirrors always produce virtual, upright and reduced images located behind the mirror; placing an object at any position (including at the focal length measured virtually) gives such an image.