Question

please show work and reasoning

1) What happens to a light wave with velocity v = ??, when it travels from air into
glass? (a) Its speed remains the same. (b) Its speed increases. (c) Its
wavelength increases. (d) Its wavelength remains the same. (e) Its frequency
remains the same.

2) A Crystal Gyser

Answer 1

Part1 : First, we know that the definition for refractive index n is:

n = c/v

where c is the speed of light in a vacuum, and v is the speed of light in the material with that refractive index.

so, we see that, because glass has a higher refractive index than air, we need to 1) increase c, or 2) decrease v.
well, c is constant, so we see that velocity of a wave must decrease when entering a medium with a higher refractive index, such as air-to-glass.
next, we know that the definition of velocity v is:
v = frequency * wavelength
from this, we see that frequency must remain constant, as otherwise there will be discontinuity between mediums (for example, an ocean wave is always smooth and continuous). So, if velocity decreases, wavelength must decrease as well.
So, thus we see that:

frequency1 = frequency2
wavelength1 < wavelength2
speed1 < speed2.

Part3 ; The part of the telescope that gathers the light, called the objective, determines the type of telescope.

A refractor telescope uses a glass lens as its objective. The glass lens is at the front of the telescope and light is bent (refracted) as it passes through the lens.

The reflector telescope uses a mirror as its objective. The mirror is close to the rear of the telescope and light is bounced off (reflected) as it strikes the mirror.

Refracting telescope generally has one big convex lens at the front which is referred to as the objective, and another smaller lens at the back which is referred to as the eyepiece. The Figure below shows how a reflecting telescope uses a carefully shaped, curved mirror to gather and concentrate a beam of light. The mirror is constructed so that all light rays arriving parallel to its axis, regardless of their distance from that axis, are reflected to pass through a single point, called the prime focus. The distance between the center of the mirror and the prime focus is the focal length.  Similarly, the Figure below shows how a lens gathers light and focuses it. An image of any object in the sky is produced when the two lenses are aligned such that they are a distance of f_o+f_e apart (where f_o and f_e are the focal lengths of the objective and the eyepiece). For a reflecting telescope the objective lens is replaced by a concave mirror, and the mirror and the eyepiece have to be aligned in the same way as in the case of the refracting telescope (the mirror and the eyepiece are a distance of f_m+f_e apart, where f_m is the focal length of the mirror), although the geometry looks a little different.

Part2 : a. For a plane mirrior image falls exactly at the same distance as the object. That is 60.96 cm from the mirror.

b. The image is virtual.

c.

It's not excatly the same distance between object and mirror, object and man. [ figure is just to show you how the it seen.]

He sholud focus upto = 152.4 - 60.96 = 91.44 cm

d.

Magnification = size of the image / size of the object

since it is a plane mirror size of object and image remains same.

Magnification = 1.

e. Sign of the magnification is "-"ve (negative)

Magnification = image distance / object distance (second formulae)

here image distance and object distance are measured in opposite directions so one them will be positve and other will be negative giving magnification negative.