50 questions · timed · auto-graded
Dispersion of light is caused because different constituent colours of light offer different refractive indexes to the material of the prism.
Ray diagram showing presbyopia is as shown below:
Advanced sun-rise: When the sun is slightly below the horizon light rays coming from the sun travel from the rarer to denser medium layers of air because of atmospheric refraction of light, light appears to come from a higher position above the horizon. Thus the sun appeared earlier than actual sun rise.
Delayed sun-set: Same reason as similar fraction occurs at the sunset.
A normal eye is not able to see distinctly the objects placed closer than 25cm, without putting any strain on the eye. This is because the ciliary muscles of eyes are unable to contract beyond a certain limit. If the objects are placed at a distance of less than 25cm from the eye, then the objects appear blurred because light rays coming from the object meet beyond the retina.
Colour of sky to an astronaut: There is no atmosphere containing air in space to scatter sunlight. As there is no scattering of light in space, the scattered light does not reach the eyes and the sky appears dark instead of blue to an astronaut in outer space.
Reason: Sunlight travels longer distance at t`his time of the day, so the short wavelength colors get scattered away and the sunlight is left with only longer wavelength lights which is reddish or orange. So the sun appears reddish in colour.
Reason: Sunrays travel shorter distance at noon and contains all the wavelengths of light which combine to form white colour. This makes the colour of sun white.
Alternate Answer
During sunrise and sunset, Sun is red in color while at noon, the Sun appears white.
At the time of sunrise and sunset, the Sun is near the horizon. The rays from the Sun have to travel a much larger part of the atmosphere to reach an observer on earth. So, most of the blue light is scattered away. The red colour which has the largest wavelength is scattered the least and enters into our eyes. Hence, the Sun appears red at the time of sunrise and sunset.
At noon, the sun is nearly overhead. The sunlight has to pass through much smaller portion of Earth's atmosphere. The scattering is much less and the Sun looks white.
Cause of hypermetropia:
$\text{u}=-\alpha,\ \text{f}=?$
$\frac{1}{\text{f}}=\frac{1}{\text{v}}-\frac{1}{\text{u}}\Rightarrow\frac{1}{\text{f}}=\frac{1}{-150}-\frac{1}{-\infty}$
$\Rightarrow\frac{1}{\text{f}}=-\frac{1}{150}+\frac{1}{\infty}=-\frac{1}{150}$
$\text{f}=-150\text{cm}=-1.5\text{m}$
$\therefore\ \text{P(Power of corrective lens)}=\frac{1}{\text{f}}=\frac{1}{1.5}\\=\frac{-10}{15}=-0.67\text{D}$
So that all and not just a handful of rich and powerful people benefit from the development of these resources/ all living beings have a birthright to the available resources.
Glass slab | Glass prism |
In the case of a glass slab, the two interfaces the light ray has to pass are parallel to each other. | In the case of a prism, the two interfaces the light ray has to pass are not parallel to each each other and are inclined at an angle. |
In this case the emergent ray is also a white light because the constituents of white light which are refracted at different angles at the first interface recombine at the second interface and emerge as a single white light. | In this case, the effects of the first interface are not reversed and the colours separated at that first interface continue along different paths upon leaving the glass at the second interface. Hence we observe a spectrum on the other side. |
The horizontal field of view having one eye is 150 degree while having both eyes is 180 degree. This means that with two eyes open we can see a wider area.
Our two eyes are a few centimeters apart from each other, due to this both the eyes see the same object from two slightly different angles and send two slightly different images of the same object to the brain. The brain combines these two slightly different images to create a three dimensional picture of objects which enable us to judge the distance of objects clearly.
$\frac{1}{\text{v}}-\frac{1}{\text{u}}=\frac{1}{\text{f}}$
$\frac{1}{-50}-\frac{1}{-25}=\frac{1}{\text{f}}$
$\text{f}=50\text{cm}$
$\text{p}=\frac{100}{\text{f}}=\frac{100}{50}=2\text{D} $
$\text{P}=\frac{1}{\text{f}}$
$\text{P}=40\text{D}$
$40=\frac{1}{\text{f}}$
$\text{f}=\frac{1}{\text{40}}$
$\text{f}=0.025\ \text{meters}=2.5\text{cm}$
focal length $=2.5\text{cm}$ the radius of curvature of the lens $=2\text{f}$$=5\text{cm}$
