As the material is of refractive index-1. \({ \theta }_{ 2 }\)  is negative and \({ \theta ' }_{ 2 }\) is positive
Now \(\left| { \theta }_{ i } \right| =\left| { \theta }_{ r } \right| =\left| { \theta ' }_{ r } \right| \)
The total deviation of the out coming ray from the incoming ray is \({ 4\theta }_{ i }\) 
The ray shall not reach the receiving plate if
\(\frac { \pi }{ 2 } \le { 4\theta }_{ i }\le \frac { 3\pi }{ 2 } \)
(Angles measured clockwise from the y-axis)
\(or \ \frac { \pi }{ 8 } \le { \theta }_{ i }\le \frac { 3\pi }{ 8 } \)
From the figure
\( sin{ \theta }_{ i }=\frac { \pi }{ R } \)
\(\therefore \frac { \pi }{ 8 } \le { sin }^{ -1 }\frac { \pi }{ R } \le \frac { 3\pi }{ 8 } \)
\( orfrac { \pi }{ 8 } \le \frac { \pi }{ R } \le \frac { 3\pi }{ 8 } \)
Thus for \(\frac { R\pi }{ 8 } \le x\le \frac { 3R\pi }{ 8 } \) light emitted from the source shall not reach the receiving plate

Interference of Light. The phenomenon of redistribution of energy in a medium due to superimposition of waves from two coherent source of light is called Interference of Light.

Constructive Interference.  At points, where the crest of one wave falls the crest of the other or a through of one falls on the through of the other, the amplitude of the resulting wave becomes maximum. Hence the energy or the intensity of light at such points becomes maximum. This is called Constructive Interference.

Destructive Interference. At some other points where the through of one falls on the crest of the other or crest of one falls on the through of the other, the amplitude of the resulting waves becomes minimum. Hence the energy or intensity becomes minimum. This is called Destructive Interference.

Law of conservation of energy is obeyed. It should be clearly understood that in interference of light no light energy is destroyed. The loss of energy at the points of destructive interference appears as the increase of energy at the points of constructive interference.

28.85 cm. -27.19 cm;enlarged, erect and virtual

Diffraction of light is the phenomenon of bending of light around corners of an obstacle.
\(Now\frac { { n\lambda }_{ red }D }{ d } =\frac { (n+1){ \lambda }_{ green }D }{ d } \)
\( n6000=(n+1)5000\)
\(6n=5n+5\)
\( n=5.\)

\(\lambda =4,800\mathring { A } =4,800\times{ 10 }^{ -8 }cm\)
\( =4.8\times{ 10 }^{ -5 }cm;\)
\( D=150cm;8\beta =2\)
\(so\quad \beta =\frac { 1 }{ 4 } =0.25cm\)
\( \beta =0.25cm;d=?\)
\( \beta =\frac { D }{ d } \lambda =\frac { D\lambda }{ \beta } \)
\( =\frac { 1504.8\times{ 10 }^{ -5 } }{ 0.25 } \)
\( or =0.0288cm.\)

Radius of curvature of objectrive mirror, 
R₁ = 220 mm
\({ f }_{ 1 }=\frac { { R }_{ 1 } }{ 2 } =\frac { 220 }{ 2 } =110 \ mm\) 
Radius of curvature of secondary mirrors, R₂ = 140 mm
\({ f }_{ 2 }=\frac { { R }_{ 2 } }{ 2 } =\frac { 140 }{ 2 } =70 \ mm\) 
Distance between two mirrors, d = 20 mm from objective mirror.
Now, for secondary mirror, u = f₁ - d = 110 - 20
= 90 mm
From mirror formula,
\(\frac { 1 }{ v } +\frac { 1 }{ u } =\frac { 1 }{ { f }_{ 2 } } \Longrightarrow \frac { 1 }{ v } =\frac { 1 }{ { f }_{ 2 } } -\frac { 1 }{ u } \) 
\( =\frac { 1 }{ 70 } -\frac { 1 }{ 90 } \Longrightarrow v=\frac { 630 }{ 2 } =315\ mm\)
i.i., final image will be at 31.5 cm to the right of secondary mirror.

We know the sun is at very distance from the earth. Assuming sun as spherical, it can be considered as point sourse situated, it can be considered as point sourse at infinity.  
Due to the large distance the radius of wavefront can be considered as large(infinity) and hence, wavefront is almost plane.
         

Polaroisation. Light waves can be polarised, but sound waves cannot be polarised.

the positions of bright and dark fringes would change rapidly. The interference pattern shall not be sustained.

In a plane mirror, image formed is virtual, erect and of same size as the object. In a convex mirror, image is erect and smaller in size.
In a concave mirror, the size and nature of the image change with change in position of the object in front of it.

Yes, it can be photographed.

Convex mirror is divergent.

It is a spot at about the centre of the retina, which is most sensitive to light.