Spectroscopy Questions

[macca69831]

Unsure about to answer these questions:

1. Why is the radiation from the sun termed an electromagnetic spectrum?

2. Give explanations for the following, in simple terms:
a) Light can travel across space but sound cannot
b) You see a 'rainbow' of colours when white light is passed through a prisim
c) Iron(III) compounds are an orange-red colour but compounds of Tin are white
d) Molecular compounds can be coloured

[vexx]

uhh i may as well try these, strange questions haha.

1. well the electromagnetic spectrum is to do with what is absorbed and emitted by things, and the radiation from the sun emits light energy and hence is radiation (something emitted in rays or waves) in the spectrum.

2.
i don't know (a) sorry
b) white light is composed of all the colours so when it is passed through a prism you get a spectrum of all colours.
c) because they are absorb their complementary colours and emit the colour they don't absorb, i don't know the complementary colours by heart, but i think orange-red is green-yelllow, so it absorbs this light and emits the orange-red colour
this is same as d)

i kind've guessed..

[/0]

2
a) Sound is a mechanical wave, and requires the oscillation of particles. Light doesn't require particles, it is the oscillations of an 'electromagnetic field' - an abstract concept similar to the 'gravitational field' (you can't see it but it's there). Therefore, since there are, on average, very few particles in space, light can travel across space but sound cannot.

[naved_s9994]

Unsure about to answer these questions:

1. Why is the radiation from the sun termed an electromagnetic spectrum?

2. Give explanations for the following, in simple terms:
a) Light can travel across space but sound cannot
b) You see a 'rainbow' of colours when white light is passed through a prisim
c) Iron(III) compounds are an orange-red colour but compounds of Tin are white
d) Molecular compounds can be coloured

Part 2a. I doubt that it is part of Unit 3 Chem course. From memory though, I completed that
topic in Unit 4 Physics last year... Its about particles etc.

Not covered in Chemistry..

[naved_s9994]

2
a) Sound is a mechanical wave, and requires the oscillation of particles. Light doesn't require particles, it is the oscillations of an 'electromagnetic field' - an abstract concept similar to the 'gravitational field' (you can't see it but it's there). Therefore, since there are, on average, very few particles in space, light can travel across space but sound cannot.

Sorry! I didnt read your post, before

[fady_22]

2) a) Sound requires a medium travel in, but light does not. Therefore, in space (where there is no medium), light can travel but sound cannot.
b) When white light travels through a prism, the colours that make up the white light (i.e. that in the visible light spectrum), refract at different extents because of their different energies, and so once they leave the prism, are separated into the colours of the visible light spectrum; a "rainbow" of colours.
c) Iron (III) absorbs visible light of a particular colour that is the complement to the light reflected. As the electron arrangement of the two are different, the light absorbed to would promote electrons to a higher energy level in the two ions would be of different energies, and thus different wavelengths and frequencies. This leads to a difference in colour absorbed and reflected (which is the colour we observe). Tin compounds, however, are white because the energy required to promote an electron to a higher energy level cannot be supplied by visible light, and so tin reflects all visible light (electronegativity of tin is higher than iron).
d) Molecular compounds can still absorb visible light, and electrons can be promoted to higher energy levels, just like other (e.g. ionic) compounds.

[/0]

Unsure about to answer these questions:

1. Why is the radiation from the sun termed an electromagnetic spectrum?

2. Give explanations for the following, in simple terms:
a) Light can travel across space but sound cannot
b) You see a 'rainbow' of colours when white light is passed through a prisim
c) Iron(III) compounds are an orange-red colour but compounds of Tin are white
d) Molecular compounds can be coloured

Part 2a. I doubt that it is part of Unit 3 Chem course. From memory though, I completed that
topic in Unit 4 Physics last year... Its about particles etc.

Not covered in Chemistry..

Lol I agree, it's probably not something you would need for chemistry, but since it's physics it's still cool to know xD

[vexx]

2
a) Sound is a mechanical wave, and requires the oscillation of particles. Light doesn't require particles, it is the oscillations of an 'electromagnetic field' - an abstract concept similar to the 'gravitational field' (you can't see it but it's there). Therefore, since there are, on average, very few particles in space, light can travel across space but sound cannot.

ooo interesting i had no idea about that!

[kyzoo]

Unsure about to answer these questions:

1. Why is the radiation from the sun termed an electromagnetic spectrum?

2. Give explanations for the following, in simple terms:
a) Light can travel across space but sound cannot
b) You see a 'rainbow' of colours when white light is passed through a prisim
c) Iron(III) compounds are an orange-red colour but compounds of Tin are white
d) Molecular compounds can be coloured

xD this is Unit 2 Physics

1.)

Because the radiation from the sun fits the criteria of an electromagnetic wave: It is self-perpetuating due to it being made of an electric field and a magnetic field that are perpendicular to each other, and hence cause each other to continuously oscillate.

2.a)

Sounds requires a medium to travel through, such as air particles. Sound cannot travel across space, which is a vacuum devoid of particles. Light on the otherhand, is a self-perpetuating wave that does not require a medium to travel through.

(I would also add that light is self-perpetuating since it is composed of continuously oscillating magnetic and electric fields that are perpendicular to each other and hence perpetually propel each other, however the question says to give the explanations in simple terms lol).

b.)

White light is a mixture of the colours of the rainbow (the visible light spectrum). Since each colour of light has a different wavelength, therefore each colour of light bends (refracts) to different extents when travelling from air into the glass prism. Hence when white light strikes a glass prism, it is separated into a "rainbow" of colours

c.)

Iron (III) ions absorb the complement of "orange-red", hence it transmits orange-red which causes it to appear orange-red. This is because the electron levels of Iron(III) are such that the difference between two electron energy levels is equivalent to the energy of the "complement of orange-red" coloured light. Tin, on the other hand, appaers white since it reflects all light. As to why it reflects light...I don't know lol.

d.)

Really, the same thing as Iron (III) ions being coloured orange-red

[iffets12345]

Yea... half of it doesn't really sound chemistry-related.