Effect of light and sound to opaque object

[songoku]

Homework Statement

An opaque object 10 cm wide casts a shadow when placed in a beam of light but has little effect on a beam of sound emitted by a small source of frequency 500 Hz. This is because
a. sound is a pressure wave whereas light is an electromagnetic waves
b. sound travels much more slowly than light
c. sound waves are longitudinal whereas light waves are transverse
d. sound waves have a much longer wavelength than light waves
e. the power per unit area in a beam of sound is much lower than that in a beam of light

Homework Equations

Don't know

The Attempt at a Solution

I don't know the relation between the choices and the question. I know that sound is longitudinal and light is transverse, I know the speed of sound and light. But I don't know how to use the info to answer the question.

Thanks

 

[ehild]

Think of the difference of wavelengths and Huygens–Fresnel principle and diffraction of waves.

ehild

 

[abhishek ghos]

with a huge wavelength in the case of sound wave as compared to light waves,the pressure waves can really move over the edges of the object.

 

[songoku]

Think of the difference of wavelengths and Huygens–Fresnel principle and diffraction of waves.

ehild

I read a little about Huygens-Fresnel principle at wiki.
"The Huygens–Fresnel principle is a method of analysis applied to problems of wave propagation (both in the far field limit and in near field diffraction). It recognizes that each point of an advancing wave front is in fact the center of a fresh disturbance and the source of a new train of waves"

But I still don't know how to relate it with the question. Huygens-Fresnel principle says that there will be a new center of disturbance. So when the sound hits the opaque object, there will be a new center of disturbance at the object's surface. Why don't the sound being reflected?

with a huge wavelength in the case of sound wave as compared to light waves,the pressure waves can really move over the edges of the object.

OK, based on your hint, I think the answer is (d). But why with a huge wavelength in the case of sound wave as compared to light waves,the pressure waves can really move over the edges of the object?

Thanks

 

[rwisz]

for your question! Based on the information given, we can infer that the main reason for the difference in effect of light and sound on the opaque object is due to the difference in their properties. Sound is a pressure wave, meaning it travels through molecules of a medium, while light is an electromagnetic wave that can travel through a vacuum. This difference in medium and mode of propagation can result in different interactions with the opaque object. Additionally, sound waves travel much slower than light waves, which can also affect their interaction with the object. Furthermore, sound waves have a longer wavelength compared to light waves, which can also contribute to their differing effects on the object. Lastly, the power per unit area in a beam of sound is much lower than that in a beam of light, which can also play a role in the observed differences. Overall, it is the combination of these factors that results in the opaque object having a greater effect on light compared to sound.