A yellow filter allows only yellow colour to pass through it. A leaf looks green because leaf reflects green colour and absorbs the rest. Thus, the yellow light passing through the filter will be absorbed by the green leaf. Thus, no colour will be reflected by the leaf making it appear black.

The path along which light travels is called a Ray.

1. Plane mirrors don't usually form real images They form virtual images of real objects. However, things can be arranged so that a plane mirror does form a real image. A convergent light beam can do this. So the answer is "convergent"

2. When at convergence point, a convergent beam of light is incident on the plane mirror, a real image is formed at the point

it selects the path that takes the least time.

When a red glass is heated to a high temperature it will glow with green light.

Objects can pnly be seen when light falls onto the object and is reflected back to our eyes to form an image on the retina.

A light ray is a narrow beam of light that is moving in a defined direction. Alternatively, a beam of light consists of lot of light rays parallel to each other.

We can only see objects when light falls into are eyes after being reflected from the objects.

We can only see objects when light reflected from the object falls on our eyes.

Light does not require a medium to propogate. Ex: The rays from the sun.

The object, that allows no light to pass through, is called Opaque.

The path along which light travels in a homogeneous medium is called a ray of light

Light is an electromagnetic wave which is transverse in nature. It does not require any material medium to pass through and can travel through vacuum.

Moon does not emit its own light. It reflects the light incident on it from the Sun. So, Moon is a non-luminous body.

Light is an electromagnetic wave which is transverse in nature. So, it does not require any material medium to pass through. Light, thus, can travel through vacuum.

A green leaf can only reflect green light, so when red light is incident on it, the leaf will not be able to reflect any light making it look black

Definition:- The path a traced by light is called a ray of light. 

Irregular reflection makes us see all the objects and everything around us. If light gets regularly reflected then every object would act like a mirror and our surroundings would be illuminated. This would have a blinding effect on eyes making it harder for us to see.

0.6328 $\mu m$ = $6328 \mathring A$
This is wavelength of red colour. So, this light will be absorbed by green pigments. 
The leaf will appear black.