Quick Review Flashcards - Click to flip and test your knowledge!
Question
The change in the direction of the path of light when it passes from one transparent medium to another is called _____.
Answer
Refraction
Question
What is the speed of light in a vacuum (approximately in $m\,s^{-1}$)?
Answer
$3 \times 10^8\,m\,s^{-1}$
Question
How does the speed of light change when it travels from a rarer medium to a denser medium?
Answer
The speed of light decreases.
Question
Why is kerosene considered optically denser than water despite having a lower mass density?
Answer
Optical density depends on the speed of light in the medium, not the inter-molecular separation of mass.
Question
When a ray of light travels from an optically rarer medium to a denser medium, how does its path change relative to the normal?
Answer
It bends towards the normal.
Question
What is the formula for the deviation ($\delta$) of a light ray passing from a rarer to a denser medium?
Answer
$\delta = i - r$
Question
Under what condition of incidence does a ray of light pass through a boundary between two media without bending?
Answer
When the ray is incident normally (angle of incidence $i = 0^{\circ}$).
Question
The first law of refraction states that the incident ray, the refracted ray, and the normal at the point of incidence all lie in the same _____.
Answer
Plane
Question
State the mathematical expression for Snell's law of refraction.
Answer
$\frac{\sin i}{\sin r} = \text{constant}$ (also expressed as $_1\mu_2$)
Question
What physical property of light remains constant when it passes from one transparent medium to another?
Answer
Frequency
Question
How is the refractive index of a medium ($\mu$) defined in terms of the speed of light?
Answer
$\mu = \frac{\text{speed of light in vacuum or air }(c)}{\text{speed of light in that medium }(V)}$
Question
The refractive index of a transparent medium is always greater than _____.
Answer
One ($1$)
Question
What is the relationship between the wavelength in a medium ($\lambda'$) and the wavelength in vacuum ($\lambda$)?
Answer
$\lambda' = \frac{\lambda}{\mu}$
Question
How does an increase in the temperature of a medium typically affect its refractive index?
Answer
The refractive index decreases as the temperature increases.
Question
Which colour of visible light travels fastest in a transparent medium like glass?
Answer
Red light
Question
Concept: Principle of Reversibility of light
Answer
Definition: The path of a light ray is reversible; if refraction occurs from medium 1 to 2, the reverse path from 2 to 1 follows the same line.
Question
What is the relationship between $_1\mu_2$ and $_2\mu_1$?
Answer
$_1\mu_2 \times _2\mu_1 = 1$ (or $_2\mu_1 = \frac{1}{_1\mu_2}$)
Question
What happens to the direction of an emergent ray when light passes through a rectangular glass block with parallel sides?
Answer
The emergent ray is parallel to the incident ray but laterally displaced.
Question
The perpendicular distance between the path of an emergent ray and the original direction of the incident ray is called _____.
Answer
Lateral displacement
Question
How does the thickness of a glass block affect the lateral displacement of light passing through it?
Answer
Lateral displacement increases with the thickness of the medium.
Question
When viewing a thick plane glass mirror, which of the multiple images formed is typically the brightest?
Answer
The second image
Question
Concept: Prism
Answer
Definition: A transparent medium bounded by five plane surfaces with a triangular cross-section.
Question
In a prism, the angle between the two refracting surfaces is known as the _____.
Answer
Angle of the prism ($A$)
Question
State the relationship between the angle of a prism ($A$) and the internal angles of refraction ($r_1$ and $r_2$).
Answer
$A = r_1 + r_2$
Question
What is the formula for the angle of deviation ($\delta$) in a prism in terms of incidence, emergence, and the prism angle?
Answer
$\delta = (i_1 + i_2) - A$
Question
At the position of minimum deviation, how is the refracted ray inside an equilateral prism oriented relative to the base?
Answer
The refracted ray is parallel to the base of the prism.
Question
What is the specific condition for the angle of incidence ($i_1$) and angle of emergence ($i_2$) at the position of minimum deviation?
Answer
The angle of incidence is equal to the angle of emergence ($i_1 = i_2$).
Question
How does the angle of deviation in a prism change when the refractive index of the prism material increases?
Answer
The angle of deviation increases.
Question
An object placed in a denser medium, when viewed from a rarer medium, appears to be at a _____ depth than its real depth.
Answer
Lesser (or shallower)
Question
What is the formula for refractive index ($\mu$) in terms of real and apparent depth?
Answer
$\mu = \frac{\text{Real depth}}{\text{Apparent depth}}$
Question
How is the 'shift' of an object defined in the context of real and apparent depth?
Answer
$\text{Shift} = \text{Real depth} - \text{Apparent depth}$
Question
Why do stars appear to twinkle in the night sky?
Answer
Due to fluctuations in the refractive index of the various layers of the atmosphere.
Question
How does the apparent depth of a pond change as the refractive index of the liquid in it increases?
Answer
The apparent depth decreases (the pond appears shallower).
Question
Concept: Critical Angle ($C$)
Answer
Definition: The angle of incidence in a denser medium for which the angle of refraction in the rarer medium is $90^{\circ}$.
Question
State the formula relating the refractive index ($\mu$) and the critical angle ($C$).
Answer
$\sin C = \frac{1}{\mu}$
Question
What phenomenon occurs when light travels from a denser to a rarer medium at an angle of incidence greater than the critical angle?
Answer
Total internal reflection
Question
Name the two essential conditions for total internal reflection to occur.
Answer
1. Light must travel from a denser to a rarer medium. 2. The angle of incidence must be greater than the critical angle.
Question
Why is a total reflecting prism preferred over a plane mirror in optical instruments like binoculars?
Answer
Because it reflects $100\%$ of light energy without losses from absorption or deterioration of a silvered surface.
Question
What is the critical angle for a glass-air interface if the refractive index of glass is $1.5$?
Answer
Approximately $42^{\circ}$
Question
What is the critical angle for a water-air interface if the refractive index of water is $1.33$?
Answer
Approximately $49^{\circ}$
Question
In a $45^{\circ}, 90^{\circ}, 45^{\circ}$ prism, how must a ray be incident to be deviated by $180^{\circ}$?
Answer
Normally on the hypotenuse face.
Question
An 'erecting prism' is a $45^{\circ}, 90^{\circ}, 45^{\circ}$ prism used to turn an inverted image upright without deviation. Where is the light incident in this case?
Answer
Parallel to the hypotenuse face (striking one of the $45^{\circ}$ faces).
Question
How does the critical angle for a pair of media change as the wavelength of light increases?
Answer
The critical angle increases with the wavelength of light.
Question
Which optical device uses total internal reflection to transmit light signals over long distances without energy loss?
Answer
Optical fibre
Question
What happens to the shift of an object if its real depth in a denser medium is increased?
Answer
The shift increases proportionally to the real depth.
Question
A stick partially immersed in water appears bent at the surface because light from the immersed part bends _____ the normal upon entering the air.
Answer
Away from
Question
In a thick glass plate, which surface is responsible for the formation of the brightest image ($A_2$)?
Answer
The lower silvered surface (due to strong first reflection).
Question
How does the refractive index of a medium relate to the speed of light within it?
Answer
The higher the refractive index, the lower the speed of light in that medium.
Question
What is the effect on the critical angle of a medium if its temperature is raised?
Answer
The critical angle increases (because the refractive index decreases).
Question
Which phenomenon causes a driver to see a 'pool of water' on a hot road in the distance?
Answer
Mirage (due to total internal reflection)