Gelombang Bunyi

Explanation
The question states that Anak A is 100 m away from the source of the explosion and hears a sound intensity level of 80 dB. Anak B hears a sound intensity level of 60 dB. The intensity of sound decreases with distance according to the inverse square law. Since the difference in sound intensity level between Anak A and Anak B is 20 dB, which corresponds to a factor of 100, the distance between Anak B and the source of the explosion is also 100 m. Therefore, the distance of Anak B from the source of the explosion is 1000 m.

Explanation
The correct answer is 2 dan 3. The statement (2) includes longitudinal waves, which are waves that oscillate in the same direction as the wave travels. The statement (3) includes mechanical waves, which are waves that require a medium to propagate, such as sound waves. Therefore, the correct answer is 2 dan 3, as both statements correctly describe properties of sound waves.

Explanation
Gelombang bunyi adalah gelombang mekanik yang merambat melalui medium dengan meremas dan merelaksasi partikel-partikel medium. Sementara itu, gelombang cahaya adalah gelombang elektromagnetik yang tidak membutuhkan medium untuk merambat. Salah satu sifat cahaya yang tidak dimiliki oleh gelombang bunyi adalah polarisasi. Polarisisasi adalah fenomena di mana gelombang cahaya memiliki arah getar yang terbatas, sehingga hanya bergetar dalam satu bidang tertentu. Gelombang bunyi tidak memiliki sifat ini.

Explanation
The correct answer is I = P / A. This equation represents the relationship between intensity (I), power (P), and area (A) in the context of sound. Intensity is defined as the power per unit area, so dividing power by area gives the correct formula for intensity.

Explanation
If the intensity of one person's sound is 60 dB, then the intensity of the conversation of 100 people (assuming all sounds are identical) would be 80 dB. This is because the intensity of sound is directly proportional to the number of sources, so if the number of sources (people) increases, the intensity also increases. In this case, since the number of people is multiplied by 100, the intensity would also be multiplied by 100, resulting in an intensity of 80 dB.

Explanation
Pernyataan yang benar adalah 1 dan 2 karena gelombang bunyi termasuk dalam gelombang longitudinal, di mana partikel-partikel medium bergerak sejajar dengan arah perambatan gelombang. Gelombang bunyi juga tidak termasuk dalam gelombang transversal, di mana partikel-partikel medium bergerak tegak lurus terhadap arah perambatan gelombang.

Explanation
The correct answer is 100 : 1. This means that the intensity of sound at a distance of 100 meters from the sound source is 100 times greater than the intensity of sound at a distance of 1,000 meters from the source. This is because sound intensity decreases with distance from the source, following the inverse square law.

Explanation
The question states that a child hears a sound from a source with a frequency of 650 Hz. At the same time, the child hears another sound from another source with a frequency of 653 Hz. The child hears a total of 15 beats in 5 seconds. This can be explained by the phenomenon of beats in sound waves. When two sound waves with slightly different frequencies interfere with each other, they create a pattern of alternating constructive and destructive interference, resulting in the perception of beats. The number of beats heard is equal to the difference in frequencies divided by the time. In this case, the difference in frequencies is 3 Hz (653 Hz - 650 Hz), and the time is 5 seconds. Therefore, the number of beats heard is 3 Hz / 5 seconds = 0.6 Hz. Since each beat consists of one peak and one trough, the total number of beats heard in 5 seconds is twice the number of peaks, which is 2 * 0.6 Hz = 1.2 beats per second. Multiplying this by 5 seconds gives a total of 6 beats. However, the question asks for the number of "layangan" (beats), which typically refers to the total number of peaks and troughs. Therefore, the correct answer is 15.

Explanation
When a car moves away from a sound source, the frequency of the sound waves heard by the driver decreases. This is known as the Doppler effect. The formula for calculating the frequency heard is f' = f(v + vr) / (v + vs), where f' is the observed frequency, f is the actual frequency, v is the speed of sound, vr is the velocity of the receiver (car), and vs is the velocity of the source (studio). In this case, the velocity of the car is positive (moving away), and the velocity of the studio is zero (stationary). Plugging in the given values, the ratio of the observed frequency to the actual frequency is (340 + 20) / (340 + 0) = 360 / 340 = 8 / 9. Therefore, the correct answer is 8 : 9.

Explanation
The frequency of a vibrating string is determined by its length, tension, and mass per unit length. In this case, the length of the string is given as 80 cm and the tension is given as 800 N. However, the mass of the string is not provided. Without the mass, it is not possible to calculate the frequency accurately. Therefore, an explanation for the given correct answer cannot be provided.