Discuss the effects of radiant energy on
our sense organs
No marks will be given for answers which do not go straight to the point, that's a good disclaimer in the start.
It's a great exam actually it's really cool.
You know I'm gonna bet that it wasn't even a correct theory because they didn't even have like
Boltzmann or believed in atoms or anything.
Hey so I have here with me an undergraduate physics exam from the
University of Sydney from 1888 and I
gave it to some 2019 physics students
also at the University of Sydney to see
if they could answer questions from 130
years ago and here's how they did.
What is the law of gravitation? on what sort of proof may be considered to rest?
That's a strange wording but I love this
question because in 1888 the concept of
gravitation that we had was Newtonian
it was entirely Newton this was before
Einstein came along in 1905 and 1915,
actually yea gravitation would have been
1915 that would have been the
general theory rather than the special one.
So the answer that we would give to this
question now would lie entirely in you
know curvature of space-time and
geodesics and all these kind of things
it wouldn't yeah like we just we know a
lot more about how the world works now
than we did in 1888 so the answer we'd
give to this question now you know the
people who are marking it, their
mind would just be blown and they'll
probably mark it wrong. I think that's
kind of cool.
Discovered that the seat,
the seat of the electrical energy of a charged conductor is
the dielectric rather than the
conductor itself.
okay I and I refuse to give a sketch.
Draw a diagram and explain the action of
an ordinary photographic camera. Why do
we fail, as a rule, in attempting to take a
photograph by gaslight?
I...I...Lens
When was the first Camera?
Well I guess by now
What does it mean by gaslight?
I've never taken a photo by gaslight so I can confirm that you still possibly fail to take photos by gaslight.
In 2019 we have CMOS sensors or CCD sensors basically you know some
light a photon of light hits a pixel and
then creates some voltage and you convert
that into an image while in 1888 it was
all done with, this must have been before film it would have been probably like
silver colloidal plates, I'm not actually
an expert in early photography.
What matters is that that sensor isn't
particularly sensitive to light you need
a lot of light to hit it to expose it
properly so I guess this goes to the
second part of the question, why do we
fail as a rule and taking photos by
gaslight? Well gaslight is relatively dim
it's probably not enough light to be
able to you know take a decent photo of.
As a tiny tangential sidenote I love the
the fact that when you look at old
photographs everyone seems to be like
really stern and not smiling and the
reason for that is because they had to
take relatively long exposures, the film
wasn't sensitive enough so it's kind of
hard to hold the smile
for 30 seconds without it blurring out.
Oh here's a good one for you Dan
a common steelyard
is graduated on the assumption that it's
weight is Q and the movable weight is
W, both which assumptions are incorrect
I know less than I started with at the beginning of the question.
What's graduated? The words are throwing me
What's a steelyard?
What's an uncommon steelyard?
What's a common steelyard?
What is a magnet? How would you make one?
Atoms have electrons around them and
each electron you can think of it as a
tiny magnet with this property called
spin and it kind of points in a
particular direction and in normal
materials like wood or you know yourself
all these spins are all in different
directions and so the net result is you
know if you're measuring the magnetism
it's zero but in special metals or other
kinds of materials you have a lot of
these spins lining up and when they line
up all these little tiny magnetic
effects add onto one another.
[offscreen] How much of that would people know in 1888?
oh that's a great question um well
because they wouldn't have quantum
mechanics. I don't think they they would
have the concept of spin or so how would
how would an 1888 student answer this
question? I guess they would say it's a
hunk of metal with these particular
properties. Was was Faraday? no
Faraday was 20th century so so I guess
that then that makes sense of that how
would you make one because that would
take advantage so they would have a
concept of electromagnetism the kind of
unification of electricity magnetism and
so you could just simply run current
through a wire and that produces a magnetic field.
Give an account of the
theory of the ordinary Bell Telephone
and explained as fully as possible how
you would make one.
how you'd make one... how you would make one, yeah the theory of the ordinary Bell
telephone, they didn't even have it.
They are very big into the experiments.
I've never even seen a telephone.
 
...what?
[offscreen] Please stop.
but first we should describe Nicholson's hydrometer
everyone is familiar with Nicholson's hydrometer
yea me
