Which of the following always form a virtual image?

Where does an object and its image coincide in a concave mirror?

$A$ ray of light is incident normally on a reflecting surface. What are the $(i)$ angle of incidence and $(ii)$ angle of reflection?

$A$ ray of light is incident obliquely on a glass slab. Draw a ray diagram showing the path of the light ray. Clearly,mark the angle of incidence,angle of refraction,angle of emergence,and lateral displacement of the ray. Give a formula to find the refractive index of the glass slab in terms of the angle of incidence and the angle of refraction.

$A$ plane mirror produces a magnification of

$(a)$ $A$ converging lens forms a real and inverted image of an object at a distance of $100 \, cm$ from it. Where should an object be placed in front of the lens so that the size of the image is twice the size of the object? Also, calculate the power of the lens.
$(b)$ State the laws of refraction.