The ratio of real depth to apparent depth is called the the:
Explanation:
$\text{refractive index} = \frac{\text{actual depth}}{\text{apparent depth}}$
Which of the following has a larger chromatic aberration?
Explanation:
Flint-glass lens has a larger chromatic aberration because the dispersive power of flint-glass is higher.
The bluish colour of water in deep sea is due to:
Explanation:
As we look deep into the sea in a direction away from the sun as the blue light is more scattered more than red. The light reaching our eyes has more of violet and blue and hence the deep sea appears blue.
How should people wearing spectacles work with a microscope?
Explanation:
If operators using a microscope usually wear spectacles (glasses) for activities such as working at their PC, they often need to remove them when looking through a microscope so they can align their eyes correctly with the eyepieces.
A convex lens of ______ focal length gives a greater magnification than lenses of _______ focal length.
Explanation:
A convex lens of short focal length gives a greater magnification than lenses of long focal length.
A short pulse of white light is incident from air to a glass slab at normal incidence. After travelling through the slab, the first colour to emerge is:
Solution:
As velocity of wave is given by the relation $\text{v}=\text{f}\lambda$. When light ray goes from one medium to other medium, the frequency of light remains unchanged. Hence $\text{v}\propto\lambda$ or greater the wavelength, greater the speed.
The light of red colour is of highest wavelength and therefore of highest speed. Therefore, after travelling through the slab, the red colour emerges first.
A manufacturer uses a concave lens instead of a convex lens in a magnifying glass by mistake. What will be the effect on the working of the lens?
Explanation:
Images formed by a concave lens are always diminished.
Beams of light are incident through the holes A and B and emerge out of the box through the holes C and D respectively as shown in the Figure. Which of the following could be inside the box?
Explanation:
Since lateral displacement is taking place in the parallel rays, a rectangular glass slab could be inside the box. Lateral displacement is the distance by which the incident light has been displaced after bending through the glass slab.
In case of a virtual and erect image, the magnification created by the mirror is:
Explanation:
Magnifaction of a mirror is defined as
$\text{m}=\frac{\text{size of image}}{\text{size of object}}$
and since, in case of virtual and errect image, size of image and object both are positive. Hence magnification created by mirror is positive.
In order to increase the angular magnification of a simple microscope, one should increase:
Explanation:
When the image is formed at infinity
m = Df = DPm = Df = DP
when the image is formed at the near point
m = (1+Df) = 1 + DP
Lateral displacement of the emergent ray of light increases with:
Explanation:
Lateral displacement produced by a glass slab of thickness t, incident on it at angle of incidence i is
Lateral displacement $ \delta=\frac{\text{t}}{\text{cosr}}\text{sin}(\text{i - r})$
Comparing real and virtual images, we may say that:
Explanation:
Real images can be obtained on a screen. On-screen rays meet in real.
Virtual images can not be obtained on a screen. Because there is no meaning of screen for the virtual image.
If a drop of water is introduced between the glass plate and a convex lens in a Newton's ring system, the ring system:
Explanation:
When a drop of water is introduced between the glass plate and a convex lens then the refractive index of the medium between them increases. So the ring system contracts in Newton's ring system.
By properly combining two prisms made of different materials, it is possible to:
Explanation:
Consider the case of prisms combined such that the refractive angles are reversed w.r.t. each other. Then, the net deviation of the yellow ray will be,
$\delta_\text{y}=(\mu_\text{y}-1)\text{A}-(\mu_\text{y}'-1)\text{A}'$
And, the net angular dispersion will be
$\delta_\text{y}-\delta_\text{r}=(\mu_\text{y}-1)\text{A}(\omega-\omega')$
Thus, by choosing appropriate conditions, we can have the above mentioned cases.
What type of lens from the following would you have in your magnifying lens to read a page in small print?
Explanation:
A concave lens always produces virtual, erect and diminished images and the decrease in the size of the image depends on the position of the object.
Concave lens will shrink the size of the already small letters. Hence, it is undesirable.
A convex lens produces real and virtual, erect and inverted, diminished, same sized and magnified image of the object, depending upon the position of the object on the principal axis.
When the object is placed at a distance less than the focal length of convex lens, an enlarged and erect image of the object is formed, which will make it easier to read small letters.
A narrow beam of white light goes through a slab having parallel faces.
Explanation:
White light will split into different colours inside the glass slab because the value of refractive index is different for different wavelengths of light; thus, they suffer different deviations. But the emergent light will be white light. As the faces of the glass slide are parallel, the emerging lights of different wavelengths will reunite after refraction.
The refraction of light is commonly known as:
Explanation:
The refraction of light is commonly known as bending.
The refracted rays bend towards the normal when they enter from rarer to denser medium.
The refracted rays bend away from the normal when they enter from denser to rarer medium.
A normal eye is not able to see objects closer than 25cm because:
Explanation:
The ciliary muscles adjust the focal length to form an image on the retina, but the muscles cannot be strained beyond a limit. Hence, if the object is brought too close to the eye, the focal length cannot be adjusted to form the image on the retina.
The phenomenon of change in the _____of light when it passes from one transparent medium to another is refraction.
Explanation:
The phenomenon of change in the path of light when it passes from one transparent medium to another is refraction. This change in path is due to the change in the speed of light in different media.
Mark the correct options:
Explanation:
This is because a real image is formed by converging reflected/ refracted rays from a mirror/ lens.
To increase the angular magnification of a simple microscope, one should increase:
The power of the lens.
Explanation:
For a simple microscope in normal adjustment, the object is placed at a distance equal to f (the focal length) from the lens, And the angular magnification is given by the relation
$\text{m}=\frac{\text{D}}{\text{f}}$
for $\text{u}<\text{f},\text{m}=\frac{\text{D}}{\text{f}}+1$
power of lens
$=\frac{1}{\text{f}}$Angular magnification depends on power.
The distance between the focus and the pole of the mirror is called:
Explanation:
The distance between the focus and the pole of the mirror is called focal length.
A printed page is seen through a glass slab place on it. The printed words appear raised. This is due to:
Explanation:
Refraction at the upper surface of the slab.
At noon the sun appears white because:
Explanation:
At noon because the sun is overhead, the light is scattered the least and hence appears white. When it is overhead, it has lesser air to travel through and the scattering from dust and other particles is reduced if the distance to be travelled in air is reduced.
A person using a lens as a simple microscope sees an:
Explanation:
A simple microscope is just a convex lens with object lying between optical centre and focus of the lens.
The distance between the extreme points on the periphery of the mirror is called:
Explanation:
Principal section is also defined as the normal 'side view' of the mirror for a ray diagram. In the diagram AB is the principal section.
Which of the following cannot be seen by a microscope?
Explanation:
A microscope is an instrument used to see objects too small for the naked eye. microscope is used to look into smaller details like the structure of the cells and the unicellular organism. On the other hand larger objects that are very far off are the targets of a telescope. hence,stars cannot be seen by a microscope.
A real image is formed by:
Explanation:
When the refracting or reflecting rays actually intersect, rather than pretending to be meeting at a point, a real image is formed. A real image hence can be obtained on a screen.
What is a virtual image?
Explanation:
When the actual rays diverge then they can never meet to form an image. Therefore the rays are assumed to meet in the backward direction of their propagation.
As the imaginary light rays meet and form the image, therefore the image can not be caught on a screen.
The line joining the pole and the centre of curvature of a mirror is called the:
Explantation:
The line joining the pole and the center of curvature of a mirror is called the principal axis.
Magnification of an optical instrument is expressed in:
Explantion:
$\text{Magnification}=\frac{\text{Image Height}}{\text{Object Height}} $
because unit of image height and object height is same hence unit of magnification is none because it is a constant number. So, it has got to unit.
The rays of different colors fail to converge at a point after going through a converging lens. This defect is called _________.
Explanation:
Chromatic aberation is the defect due to which rays of different wavelength converge at various point after passing through converging lens. It is due to varying refractive index for various wavelength.
In producing a pure spectrum, the incident light is passed through a narrow slit placed in the focal plane of an achromatic lens because a narrow slit:
Explanation:
To produce a pure spectrum, a parallel light beam is required to be incident on the dispersing element. So, the incident light is passed through a narrow slit placed in the focal plane of an achromatic lens.
Between the primary and secondary rainbows, there is a dark band known as Alexandar’s dark band. This is because:
Solution:
The Alexandar's dark band lies between the primary and secondary rainbows, formed due to light scattered into this region interfere destructively. The primary rainbows subtends an angle nearly 41º to 42º at observer's eye, whereas secondary rainbows subtends an angle nearly 51º to 54º at observer's eye w.r.t. incident light ray.
Hence, the scattered rays with respect to the incident light of the sun lies between approximately 42º and 50º.
Which of the following (referred to a spherical mirror) do (does) not depend on whether the rays are paraxial or not?
Pole.
Focus.
Principal axis.
Explanation:
If Paraxial rays comes to parallel to the spherical mirror is pasees to the Focus of the spherical mirror.
A coin kept in a container and not visible can be viewed by pouring water into the container. It happens because of the:
Explanation:
When water is poured then it is due to refraction of light the coin becomes visible. When the light rays travel from the water medium (denser) to the air medium (rarer) it bends away from the normal due to the refraction. Therefore, an image of the coin is formed at a smaller depth causing it to be visible (as shown in the figure).
The image formed behind a mirror and a virtual image:
Explanation:
The image formed behind a mirror is virtual in nature. So, they are of the same nature always.
In which of the following the final image is erect?
Explanation:
Only in simple microscope the image formed is erect, while it is inverted in compound microscope and astronomical telescope.
The size of an object as perceived by an eye depends primarily on:
Explanation:
An eye consists of a lens that works on the principle on which a glass lens works. It forms the image on the screen called retina. The magnification, in this case, depends on the ratio of the image to the object height.
A screen is placed a distance 40cm away from an illuminated object. A converging lens is placed between the source and the screen and it is attempted to form the image of the source on the screen. If no position could be found, the focal length of the lens:
Explanation:
$\text{v}=(40-4)$
$\frac{1}{\text{f}}=\frac{1}{40-4}-\frac{1}{(-\text{u})}$
$\frac{\text{df}}{\text{du}}=0$ for f minimum.
$\frac{\text{df}}{\text{du}}=1-\frac{\text{u}}{20}=0$
$\text{u}=20$
$\text{f}_{\text{min}}=10\text{cm}$
A plane mirror produces an image that is:
Explanation:
So a plane mirror always forms a virtual, upright and same sized image.
A ray of light travels from a denser to a rarer medium then, the ray:
Explanation:
When light travels from denser to rarer medium, the velocity of light increases which results in bending of light away from the normal.
When is the real image formed?
Explanation:
Real image formed when the rays of light after reflection or refraction actually converge at some point and when objects are placed outside the focal length of a converging lens or outside the focal length of a converging mirror.
Choose the correct option:
Explanation:
As shown in figure A, a virtual image is formed because refracted rays only appear to meet at the image.
As shown in figure B, a real image is formed because refracted rays actually meet at the image.
The focal length of a converging lens are fv and fr for violet and red light respectively:
Explanation:
Focal length is inversely proportional to refractive index and refractive index is inversely proportional to $\lambda^2.$ So, keeping other parameters the same, we can say:
$\text{f}\propto\frac{1}{\lambda^2}\ \ (\because\lambda_\text{r}<\lambda_\upsilon)$
$\therefore\text{f}_\text{v}<\text{f}_\text{r}$
The phenomenon of light passing through the object is called:
Explanation:
The phenomena when light passes through the object (a medium) is known as refraction. Refraction is defined as the bending of light ray when it passes from one medium to another.
A car is moving with at a constant speed of 60kmh-1 on a straight road. Looking at the rear view mirror, the driver finds that the car following him is at a distance of 100m and is approaching with a speed of 5kmh-1. In order to keep track of the car in the rear, the driver begins to glance alternatively at the rear and side mirror of his car after every 2s till the other car overtakes. If the two cars were maintaining their speeds, which of the following statement (s) is/are correct?
Solution:
We know that, the image formed by convex mirror does not depend on the relative position of object wit mirror. Therefore, the speed of the approaching car would appear to increase as the distance between the cars decreases in the side mirror.
The focal length of a normal eye-lens is about:
Explanation:
Given:
Near point of the human eye, u = -25cm
Distance between the retina and the eye lens, v = 2cm (approximately)
thus, we have the focal length, f.
$\frac{1}{\text{f}}=\frac{1}{\text{v}}-\frac{1}{\text{u}}$
$\Rightarrow\frac{1}{\text{f}}\cong\frac{1}{2}-\frac{1}{-25}$
$\Rightarrow\frac{1}{\text{f}}\cong\frac{27}{50}$
$\Rightarrow\text{x}\cong2\text{cm}$
A magnifying glass is used to read the newspaper. As it is moved far away from the newspaper:
Explanation:
As the magnifying lens(convex lens) is moved far away from the eye, the image formed is real and inverted and is formed inside the human eye and hence it blurs. Since the object is far away from the mirror, the image formed is diminished and hence magnification reduces.
When light travels from one medium into another it suffers:
Explanation:
When light travels from one medium into another it suffers refraction.