Science M.C.Q. [I MARKS]

 Vitamin $A$ deficiencies occur from fat malabsorption, liver disorders and inadequate food intake.

The relationship between no. of images and angle of mirror is
$\text{Images}=\Big(\frac{360^\circ}{\text{angle between the mirrors}}\Big)-1$
$\text{Images}=\Big(\frac{360^\circ}{90^\circ}\Big)-1$
Images $= 4 – 1$
Images $= 3$

 Blindness is caused primarily because of the defect in the cornea. Hence, statement $IV$ is incorrect.

 The least distance of distinct vision means the minimum distance for an object to be viewed clearly. This minimum distance for a young adult with normal vision is $25\ cm.$

 Since $OS$ is normal to the mirror $AB.$

$\therefore\angle\text{i}_1=45^\circ, $ also $\angle\text{r}_1= 45^\circ$ in
$\Delta\text{CQR}, \angle\text{C} = 90^\circ, \angle\text{CQR} = 45^\circ$
$\therefore\angle\text{CQR} = 45^\circ$
$\big[$$\therefore$ sum of all the three angles in tringle is $180^\circ$$\big]$
Hence, $\angle\text{i}_2 = 45^\circ$
$\big[$ TR is the normal to the mirror BD$\big]$
$\therefore\angle\text{r}_2 = 45^\circ$

 The angle between the incident ray and the mirror is $30$ degrees.
Angle of incidence = angle of reflection.
$90$ degrees is going directly into the mirror.
So, $90 – 30 = 60$ degrees.
The total angle between the incident ray and the reflected ray will be $120$ degree.

Bulbs $P$ and $Q$ lies in the plane of incidence of mirror while bulb $R$ does not. Thus, only the images of the bulbs $P$ and $Q$ can be seen by the observer from the plane mirror.

The point nearest to the eye at which an object is distinctly visible is called the near point of the eye. The distance of the near point of the eye is called the least distance of distinct vision. It varies with age. For an infant, it is $5$ to $8\ cm,$ for an adult, it is $20$ to $25\ cm.$

Angle of incidence is always equal to angle of refection. Hence, angle of reflection will be $35^\circ .$

 Height of the lower edge from ground $= h/ 2, h \rightarrow $ height of eyes from ground.

We know that for a reflected ray, the angle that the incident ray makes with the line perpendicular to the surface is equal to the angle made by the reflected ray with this perpendicular line. $N$ is the correct reflected ray of $X.$

 Object distance $= 150\ cm$
$\therefore$ Image distance $= 150\ cm$ (as in plane mirror, object distance is always equal to the image distance)
The patient is $100\ cm$ away from the mirror.
So, the distance between the patient's eyes and the image $= 100\ cm + 150\ cm = 250\ cm$

 Object distance after shifting the object $= 4\ m + 0.5 \ m = 4.5\ m$ For a plane mirror;
Object distance = Image distance $= 4.5  \ m$
Distance between the object and its image $= 4.5 + 4.5 = 9\ m.$

 The diameter of the eye ball is approximately $2.3\ cm.$
Images are formed on the retina of the normal eye, which is approximately $2.3\ cm$ behind the pupil.The formation of an image $3\ cm$ away from the pupil of the eye indicates that the light rays are focused behind the retina. For proper visibility, the light rays must focus on the retina.

It can be concluded that Shyam is suffering from hypermetropia and a convex lens can be used to correct this defect.

A concave mirror is used by $E.N.T.$ doctors to get a magnified image of internal organs like ear, nose and throat.

$ T$ is a laterally symmetrical object and hence its image in a plane mirror would be the same as itself.

 The impression or sensation remains on the retina for about $1/16th$ of a second even after removal of the object.

 Following the laws of reflection of light, in case $A,$ when a ray of light from the bulb strikes the mirror $M,$ it will get reflected back such that the angle of incidence is equal to the angle of reflection.

 For a plane mirror, the image distance = object distance. Therefore, the image is formed at a distance of $10\ cm$ from the mirror on the other side.

 According to the law of reflection, the angle of incidence is equal to the angle of reflection. If the incident ray makes an angle of $65$ degree with the surface of plane mirror, than the angle of incidence can be calculated as: angle of incidence $= 90 –$ angle made with the plane mirror $= 90 – 65 = 25$ degree. Since, the angle of incidence is equal to the angle of reflection, therefore the required angle of reflection $= 25$ degree.

 Length of the plane mirror required is $H/ 2,$
$H =$ height of object.