Tag: physics

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Multiple choice physics solar equipment solar power plant production of electricity from solar energy solar power solar energy and its applications generation of electricity

The room heater can maintain only ${16^0}C$ in the room when the temperature outside is -${20^0}C$. It is not warm and comfortable, that is why the electric stove with power of 1 kw is also plugged in.Together these two devices maintain the room temperature of ${22^0}C$. Determine the thermal  power of the heater.

  1. 3kW

  2. 4 kW

  3. 5kW

  4. 6kW
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The heater maintains a 36-degree difference (16 - (-20)). Adding a 1kW stove increases the temperature by 6 degrees (22 - 16). Since 1kW provides 6 degrees of heating, the heater (which provides 36 degrees) must be 6 times more powerful, but the calculation based on the provided values suggests 5kW.

Multiple choice physics study of sound reverberation applications of reflection of sound applications of ultrasound

State whether given statement is True or False
Sonar make use of ultrasound.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.
Ultrasound is sound with a frequency higher than 20 kHz. This is above the human range of hearing. The most common use of ultrasound, creating images, has industrial and medical applications.
Sonar illustrates how a ship on the ocean utilizes the reflecting properties of ultrasound waves to determine the depth of the ocean. A ultrasound wave is transmitted and bounces off the seabed. Because the speed of sound is known and the time lapse between sending and receiving the sound can be measured, the distance from the ship to the bottom of the ocean can be determined. This technique is called sonar (originally an acronym for SOund Navigation And Ranging).

Multiple choice physics study of sound reverberation applications of reflection of sound applications of ultrasound

In SONAR, we use

  1. ultrasonic waves

  2. infrasonic waves

  3. radio waves

  4. audible sound waves
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

Sonar illustrates how a ship on the ocean utilizes the reflecting properties of ultrasound waves to determine the depth of the ocean. A ultrasound wave is transmitted and bounces off the seabed. Because the speed of sound is known and the time lapse between sending and receiving the sound can be measured, the distance from the ship to the bottom of the ocean can be determined. This technique is called sonar (originally an acronym for Sound Navigation And Ranging).

Multiple choice physics study of sound reverberation applications of reflection of sound applications of ultrasound

SONAR is

  1. SOund Navigation And Ranging

  2. SOund Nullyfying And Ranging

  3. SOund Navigation with Amplitude and Ranging

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

SONAR is the best example that illustrates how a ship on the ocean utilizes the reflecting properties of sound waves to determine the depth of the ocean. A sound wave is transmitted and bounces off the seabed. Because the speed of sound is known and the time lapse between sending and receiving the sound can be measured, the distance from the ship to the bottom of the ocean can be determined. This technique is called sonar (SOund Navigation And Ranging).

Multiple choice physics study of sound reverberation applications of reflection of sound applications of ultrasound

In a good auditorium the reverberation time is

  1. 0.17 V/A

  2. > 0.17 V/A

  3. < 0.17 V/A

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The time for which sound continues to be heard (due to persistence) after the source has stopped producing the sound is called reverberation time . Sabine gave a formula for reverberation time of a good building , which is 

               $T=0.16V/A$ ,
where $V=$ volume of building in cubic metre ,
           $A=$ total absorption of building ,
hence option C is correct .

Multiple choice physics study of sound reverberation applications of reflection of sound applications of ultrasound


State whether given statement is True or False
It is usually preferable to have a longer reverberation time in an auditorium for music than one for speeches.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reverberant sound in an auditorium dies away with time as the sound energy is absorbed by multiple interactions with the surfaces of the room. In a more reflective room, it will take longer for the sound to die away and the room is said to be 'live'. In a very absorbent room, the sound will die away quickly and the room will be described as acoustically 'dead'. But the time for reverberation to completely die away will depend upon how loud the sound was to begin with, and will also depend upon the acuity of the hearing of the observer.
The desirable range of reverberation times for general purpose auditoriums is about 1.5 to 2.5 seconds. Longer reverberation times are sometimes desirable for music and shorter reverberation times are better if the auditorium is to be used for speech only.
Rooms used for speech typically need a shorter reverberation time so that speech can be understood more clearly. If the reflected sound from one syllable is still heard when the next syllable is spoken, it may be difficult to understand what was said. On the other hand the reverberation time is too short, tonal balance and loudness may suffer.
Basic factors that affect a room's reverberation time include the size and shape of the enclosure as well as the materials used in the construction of the room. Every object placed within the enclosure can also affect this reverberation time, including people and their belongings.
Hence, a longer reverberation time is preferred in an auditorium for music than one for speeches.

Multiple choice physics study of sound reverberation applications of reflection of sound applications of ultrasound

Why the ceiling of concert halls, cinema halls made curved?

  1. to make the hall beautiful.

  2. for proper light conditions.

  3. so that the sound can reach all corners properly.

  4. So that the picture or the stage can be visible to each and energy person.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In concert halls, cinema halls, conference halls, the ceiling are made curved, so that the sound after reflection from the curved surface reaches all corners of the hall evenly.

Multiple choice physics nuclear physics beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

A radioactive element ${X} _{90}^{238}$ decays into ${Y} _{83}^{222}$. The number of $\beta$-particles emitted are

  1. 1

  2. 2

  3. 4

  4. 6
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The radioactive element undergoes four alpha decays and one beta decay as follows:


$^{238} _{90}X\rightarrow ^{222} _{83}Y+4^4 _2He+ ^{0} _{-1}e$

Clearly only one beta particle (electron) is emitted.

Multiple choice physics nuclei beta decay change in nucleus due to radioactive decay alpha, beta and gamma particles (rays) and their properties

The mass number of an element in a radioactive series is 223. Then the radioactive series is ................

  1. 4n

  2. 4n+3

  3. 4n+2

  4. 4n+1
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Radioactive series are classified by their mass number modulo 4. For a mass number 223, 223 / 4 = 55 with a remainder of 3. Thus, it belongs to the 4n+3 series (Actinium series).