1. A right angle is the angle 90. So the light wave will be reflected the exact way it came.

2. Concave Lenses makes the light to spread out. The lights don't meet. So a Concave Lens doesn't have a focal point.

1. It is said in the book that refraction occurs because one side of the wave reaches the new medium slightly before the other side does. However, when a light wave strikes glass at a right angle, all of the waves reach the medium at the same speed, thus there is no difference. Therefore, the light will reflect and bounce off the glass the same way it reached the medium, forming a straight line.

2. Concave lenses do not have focal points. This is due to the shape of the lense. Concave lenses are curved inward, and cause parellel light rays to spread out instead of meeting at one point, which is the focal point. This makes it naturally impossible for the light rays to meet at a certain point, and leads to the conclusion that there is no focal point.

1. As far as I know, right angle means 90'. And I think if a light wave strikes the glass vertically, it will not be refracted and will go forward passing the glass in a straight line.

2. If you try and draw a picture of a concave lens and also draw parallel line that means light to pass through the lens, they will be refracted away from each other, and they wll never meet. But I think the focal point will be where the extension line of the two refracted lights meet.

1. Usually, when a light wave strikes the glass, refraction happens. If you look at the page 119 of this book, it says that the light wave reaches the glass at an angle other than 90, then the light wave keeps going forward in a slightly different direction and this is the refraction. So I think that the 'right angle' in the question number one means the angel 90, ad if the light wave reaches the glass at angel 90, it reflect off the surface of the glass.

2. A lens is a clear optical tool that refracts light, and there are two kinds of lens. Convex and Concave lenses. First, when the light rays passes through a convex lens, it is refracted inward. On the other hand, when the light passes through a concave lens, the light is refracted outward. Because they are refracted to the outside, the light rays which passed through the Concave lenses can't meat. So I think that Concave lenses don't have focal points.