Science (Light,Sound) - Software Development MCQ

CONCEPT

Using lens formula

Where v = image distance, u = object distance, f = focal length of the lens

In the case of a concave lens focal length is always negative be focal will always be left side of the lens.

For a convex lens focal length will always be positive.

Also, magnification for the lens

CALCULATION

Given: u = -18cm, v = ?, f = -27cm

Now calculation magnification

Hint

Sign convention for lens formula

• ​The length measured from the optic center to the right-hand side is “positive (+ve)”
• The length measured from the optic center to the right-hand side is “negative (-ve)”.
• All the distance is measured from the optic center only.
• The focal length for the concave lens is negative and for the convex lens is positive.

The point where incident rays passes through a point on the principal axis is called first focus.

• When a ray of light passing through a principal focus, after refraction from a convex lens, will emerge parallel to the principal axis.
• When ray of light crossing through a principal focus, after refraction from a convex lens, will appear parallel to the principal axis. A ray of light developing to match at the principal focus of a concave lens, after refraction, will develop parallel to the principal axis.
• One ray of light becomes parallel to the principal axis of the lens and thus, passes through another focus after refraction through the lens. Another ray of light passes through the optical centre of the lens and goes straight. Therefore, the image formed is: At infinity, Real and inverted, highly enlarged.
•  

So, the correct answer is Option-1-after refraction it emerges parallel to the principal axis.

Concept:

• During the day the sun heats up the earth's surface, warming the air close to the ground. 
• Sound travels faster in warmer air. So the sound travels faster in the air close to the ground.
• The reverse happens at night.
• The speed of the sound in air is given by, $v=\sqrt{\frac{\gamma RT}{M}}$ where M = molecular mass of the air, R = Universal gas constant, T = temperature, γ = adiabatic index
• In terms of density, speed, , where β = bulk modulus, ρ = density

Explanation:

The speed of the sound in air is given by, 

In terms of density and bulk modulus,  

From the above expression, the speed of the sound is depended on the following factors,

• The temperature
• density: The composition of the air and the humidity(moisture) change the density 
• The speed is almost independent of the atmospheric pressure.

The correct answer is Light.

Key Points

• The dark circle in the iris's middle is the pupil of the eye.
• The colorful part of the eye, or iris, has a structure and hue that are particular to each individual.
• A portal that admits and controls the flow of light to the retina is the pupil of the eye.
• This step in the process contributes to how one see images.
• To regulate the amount of light allowed to enter the eye, the pupil opens and closes.
• Light enters the eye from the outside and travels through the pupil before passing through the transparent lens.
• This light is then focused on the retina, which is the layer of light sensitive cells at the back of the eye.
• Pupils expand or dilate to let in more light when it is dark.
• By doing this, vision is enhanced.
• pupil contracts to a very small diameter in strong light to shield our retina's delicate photoreceptors.
• In response to outside light, the pupil adjusts in size. 

​

Explanation:

There are two types of spherical lenses:

Convex lens:

• A convex lens is thick in the middle and thin at the edges.
• A convex lens is a spherical lens whose two surfaces are bent outwards.
• A convex lens is also know known as a converging lens.

Concave lens:

• A concave lens is thin in the middle and thick at the edges.
• A concave lens is a spherical lens whose two surfaces are concave or bent inward.
• A concave lens is also know known as a diverging lens.
• A concave lens makes close-up objects smaller.

Variations of these two are

Additional Information

There are two types of spherical mirror:

Convex mirror:

• The spherical mirror whose reflecting surface is away from the centre of curvature is called a convex mirror.
• It always from a virtual image of any object.

Concave mirror:

• The mirror whose reflecting surface is inward is called a concave mirror.
• It can form both real as well as virtual image of any object.

• If the light from the point source is headed over the concave mirror, then it is collimated (made parallel) to infinite.​

Telescope:

• Reflecting telescopes are also called reflectors.
• Most telescopes used by astronomers today are reflectors.
• Most common reflecting telescopes are a variation of the Newtonian telescope.
• It consists of a large concave mirror as objective and convex mirror as the eyepiece.

Concept:

• The ear is a sense organ that detects and transmits sounds and also maintains a sense of balance.
• The ear consists of three parts - external ear, middle ear, and internal ear.
• The External ear has 3 parts- pinna, external auditory meatus, and tympanic membrane.
• The Middle ear has 3 parts- tympanic cavity, the Eustachian tube, and ear ossicles.
• The Inner ear comprises two parts- bony labyrinth and membranous labyrinth.

Important Points

• The membranous labyrinth of inner ear contains sensory receptors responsible for balance and hearing.
• The membranous labyrinth is filled with endolymph and has three semi-circular ducts, cochlear duct, saccule, and utricle.
• The part of internal ear responsible for hearing is the cochlea.
• It is one of the parts of the membranous labyrinth.
• The cochlea is spiral-shaped, coiled, hollow bone that controls the auditory transduction process.
• Auditory receptors are located in it.
• Cochlea transforms auditory signals into neural impulses that are then transported to the brain via afferent nerve fibers and auditory nerves, where they are integrated by the brain and we recognize the sound.
  

Additional Information

• Semicircular canals are a series of interconnected tubes present in the inner ear and it is a part of bony labyrinth. 
• Utriculus is present in the inner ear and connects the cochlea to the semicircular canals.
• Sacculus contains sensory cells of the inner ear and recognizes linear accelerations and head tilts in the vertical plane. 

Hence, the correct option is (1) Cochlea.

Neon lighting

• Neon lighting consists of brightly glowing, electrified glass tubes or bulbs that contain rarefied neon or other gases. Neon lights are a type of cold cathode gas-discharge light.
• A neon tube is a sealed glass tube with a metal electrode at each end, filled with one of a number of gases at low pressure.
• A high potential of several thousand volts applied to the electrodes ionizes the gas in the tube, causing it to emit colored light.
• The color of the light depends on the gas in the tube.
• For lighting purposes, the maximum tube size is approximately 5m long and 25mm in diameter.
• Due to safety concerns, inefficiency, and expense, the popularity of neon signage has waned over the years in favor of incandescent and LED signs. LED is now the primary source of lighting in illuminated signage as it is the most efficient.

Concept:

Effect of temperature For one mole of gas, PV = RT. If M is the molecular weight of the gas, then,

 or 

Substituting the value of V in the gas equation, we have,

 or 

∴ v ∝ √T

Hence the velocity of sound in a gas is directly proportional to the square root of its absolute temperature.

Thus if V₁ and V₂ are the velocities of sound in gas at absolute temperatures T₁ and T₂ respectively, then,

Explanation:

Given;

Additional Information
The velocity of sound in a gas is given by :

It is interesting to compare this result with the r. m. s. speed of the molecules of a gas viz,

The correct answer is Neither 1 nor 2 is true.

Key Points

• In Nickel speed of sound is 6040 m/s.
• In Aluminium, the speed of sound is 6420 m/s.
  • Hence option 1 and 2 both are not true.

Additional Information

• The speed of sound in a medium depends:
  • The temperature of the medium.
  • The speed of sound decreases when we go from solid to a gaseous state.
  • In any medium, as we increase the temperature the speed of sound increases.
  • The velocity of sound through a gas is inversely proportional to the square root of the density of the gas.
• Sound is mechanical energy that produces a sensation of hearing.
  • Sound is produced due to the vibration of different objects.
  • The sound wave propagates as compressions & rarefactions in the medium.
  • Sound waves are longitudinal waves.
  • Sounds of frequencies below 20 Hz are called infrasonic sound or infrasound.
  • Rhinoceroses communicate using infrasound of frequency as low as 5 Hz.
  • Whales and elephants produce sound in the infrasound range.
  • Frequencies higher than 20 kHz are called ultrasonic sound or ultrasound.
  • Ultrasound is produced by dolphins, bats, and porpoises.

Concept:

Galilean telescope:

• It is used to see far-off objects on the earth.
• It is also a type of terrestrial telescope but of a much smaller field of view.
• In the Galilean telescope, the objective lens is a converging lens (convex lens) while the eye lens is a diverging lens (concave lens).

Hence, In the Galilean telescope, the objective lens is a converging lens (convex lens) while the eye lens is a diverging lens (concave lens). Hence, option 3 is correct.