Many spells shed light as one of their effects, such as the Sunbeam spell, which says:     For the Duration, a mote of brilliant radiance shines in your hand. It sheds bright light in a 30-foot radius and dim light for an additional 30 feet. The light is sunlight.   We know that spell effects are blocked by total cover (PHB, p.204):     A spell’s effect expands in straight lines from the point of origin. If no unblocked straight line extends from the point of origin to a location within the area of effect, that location isn’t included in the spell’s area. To block one of these imaginary lines, an obstruction must provide total cover.   And that transparent obstacles still qualify as total cover (citation needed, but I'm pretty sure about this one).  Thus it seems to be the case that a glass window (or other transparent obstruction) can block magical light. However, this seems odd when you consider non-magical light can obviously pass through it fine.   So: can light from a spell like Sunbeam pass through a window, or not?
120738
If I cast light on a small pebble and placed it in a sealed, transparent glass jar would it emit light outside of the jar?  The reason I am asking is because the rules for areas of effects say:     A spell’s effect expands in straight lines from the point of origin. If no unblocked straight line extends from the point of origin to a location within the area of effect, that location isn’t included in the spell’s area. To block one of these imaginary lines, an obstruction must provide total cover.   That means that the jar (which provides total cover) would prevent anything outside of the jar from being in light's area of effect. So, it seems to me that the rules imply that nothing outside the jar would be illuminated.  This actually does have potential mechanical implications in the game as can be seen in this question: .   Am I missing something here or is this just an example of the rules creating a nonsensical effect?
14107
I created a glass cone with black seams (the seams are a diffuse not transparent material).    When I shine light on it, the cone casts a solid shadow. Why is this?   I would like to have a (semi) transparent shadow cast from the glass and a full shadow from the seams.  Here is the link where you can (hopefully) download the blend file:
45656
When you cast the solid-box variant of , the spell specifies:     A prison in the shape of a box can be up to 10 feet on a side, creating a solid barrier that prevents any matter from passing through it and blocking any spells cast into or out of the area.   Clearly this stops a single-target spell like  from affecting anything inside the box if it's cast from outside the box.   But does it stop an area-of-effect spell like  or , cast on a point just outside the box, from affecting creatures or objects within the box?
5281
The book I'm reading about optics says at some point that "each color (wavelength) contained in the white light interferes only with itself". But why is this so?  Edit: I moved the rest of the question .
66461
One of the great 'coincidences' in physics is that the Sun happens to shine most brightly at exactly the wavelengths our eyes can see; it's an easy explanation that our eyes evolved to make the most out of what was available.  However, this spectral window is also , with Rayleigh scattering and the ozone layer protecting us from the UV and strong water vapour absorption in the IR until way into the radio range.  My question is: is this a coincidence? Were there geological factors that made it so? Or is it just lucky chance? (I also notice other planets in our neighbourhood weren't quite so lucky.) Or had atmospheric absorption been different our eyes would have tuned to whatever spectral window were brighter as a whole?
33179
I have been having a discussion regarding the Shape Water cantrip from the Elemental Evil Player's Companion. A friend and I are trying to come to an accurate view of how this spell actually functions.   Some example questions:   Must the targeted water be within a 5 foot cube area, or does it need to be of a volume not exceeding 125 cubic feet? If you shape water that is within a 5 foot cube, can the final shape you animate it to extend outside the cube? Can you cause the shaping to affect ice and snow, or only liquid water? Would you be able to carry a globe of water alongside you over distances?   Really, there are two parts:    What can be targeted by the spell? What are the limitations on the 'shape and animate' portion of the spell?   The answer I am looking for, if possible, would use the language of the spell, possibly with precedent from other game text, to clearly define the limitations of this cantrip.
103540
Related:   If you are standing in front of a glass window during the day, you can see your dim white t-shirt’s reflection in the window. The reflection is dim because only 4% of the light is reflected (assuming you’re perpendicular to the window) while the rest is transmitted through the glass.  If a white object is placed in front of this glass pane, it’s obvious that white light is reflected as white and not colored. Why is this?   I vaguely remember that visible light that is reflected penetrates glass about λ/2, so that means that blue light penetrates the least while red light penetrates more. If I shine white light onto a glass window (assume RGB color model), I have to account for all three colored scatterers in roughly equal amounts of intensity to produce white. Here is what I think.  • Blue light penetrates shorter distances into the glass window’s atomic layers and recruits less atomic scatterers that back scatter more intensity blue light. I assume Rayleigh scattering is valid since wavelengths of light are much greater than the atomic spacing’s in glass, therefore $I ∝ 1/λ^4$.  • Green light penetrates deeper into the glass window’s atomic layers and recruits more atomic scatterers that back scatter more “less intensity” green light according to $I ∝ 1/λ^4$?. So the larger number of green atomic scatterers scattered less intense green light but there are more green atomic scatterers.  • In a similar fashion, red light would recruit an even larger number of red atomic scatterers (but less intense than green or blue), however, the increased number of red atomic scatterers compensates for a more overall intense red intensity.   In summary, there are roughly equal amounts of blue, green and red light reflected such that a glass window reflects white objects white. Here is what I am asking: is this correct way to view this? I was unable to find this anywhere online or on . I would greatly appreciate feedback, especially if this is not correct.
13802
If light is passed through two polarizing filters before arriving at a target, and both of the filters are oriented at 90° to each other, then no light will be received at the target. If a third filter is added between the first two, oriented at a 45° angle (as shown below), light will reach the target.  Why is this the case? As I understand it, a polarized filter does nothing except filter out light--it does not alter the light passing through in any way. If two filters exist that will eliminate all of the light, why does the presence of a third, which should serve only to filter out additional light, actually act to allow light through?
11235
Why is it that if I have two torches, each shining rays in perpendicular directions at perpendicular screens, such that the beams cross, then the images on the respective screens are independent of whether the alternate torch is switched on? In other words, why does light seem to pass through itself without interacting?  Apologies if this question is basic, and apologies if there is a similar question somewhere on the site but I haven't managed to find an answer.   Thanks,  A.
49697
Using the D&amp;D 5e RPG system. We'll use a  and the spell  as an example. What, if anything, occurs when you attempt to cast such a spell on a creature that is currently pregnant?  The spell specifies the following:     You attempt to send one creature that you can see within range to   another plane of existence. The target must succeed on a Charisma   saving throw or be banished. If the target is native to the plane of   existence you’re on, you banish the target to a harmless demiplane.   While there, the target is incapacitated   Does the spell take effect and if so does it bring the as yet unborn creature(s) with the mother? Possible complications include, beyond the spell only targeting a single creature, that it must also be a creature that you can see. The supposition is that being inside another creature would provide those inside with .     A target with total cover can't be targeted directly by an attack or a   spell, although some spells can reach such a target by including it in   an area of effect. A target has total cover if it is completely   concealed by an obstacle
70140
Let's assume we have some PCs moving along infinitely flat plains. In the air (some distance away) is a large creature with a rider that can cast spells. In optimal conditions (so there's normal daylight and no obstructions), how far from the PCs can the rider be and still see them?   Note that I've certainly seen the Light Sources and Illumination table, but that's not helpful. We're talking about natural light sources under optimal conditions; is there an official Pathfinder rule for how far PCs and NPCs can see?
87166
I have been recently wondering, if I take a powerful enough energy source (photon) and I have an perfect mirror exactly in front of it and assume an "emitter" shot the light towards the mirror.   As perfect mirrors absorb no energy of ANY kind from photons, should this mean that the perfect mirrors would never move due to transfer of momentum of the light?
63176
During a sunny day the walls of my house warm up (no surprise). My question: how much of this warming up (if any) comes from visible light? I associate infrared with thermal energy. If my house was floating in space (to prevent any thermal exchange with its surroundings) and I installed a giant infrared (and UV) filter between it and the sun, would it still warm up (compared to its rest temperature in full darkness)?
61654
If I cast Darkness at 4th level and someone else casts Daylight at 4th level, how do the two spells interact?  I found  back in October 2014 that says the spell does not get stronger when upcast, but as is written in the Player's Handbook (p. 201):     When a spellcaster casts a spell using a slot that is of a higher   level than the spell, the spell assumes the higher level for that   casting.   Therefore, if we both cast Darkness and Daylight at 4th level, they do not dispel each other - but how would they interact when they meet each other?
81653
I have a player in my campaign who took the  tiefling racial feat (from Xanathar's Guide to Everything, p. 74-75). One of its abilities is:     Whenever you cast a spell that deals fire damage, you can cause flames        to wreathe you until the end of your next turn. The flames don’t harm        you or your possessions, and they shed bright light out to 30 feet and        dim light for an additional 30 feet. While the flames are present, any        creature within 5 feet of you that hits you with a melee attack takes        1d4 fire damage.   Additionally, he took the  cantrip:     A flickering flame appears in your hand. The flame remains there for        the duration [...]      You can also attack with the flame. When you cast this spell, or as an        action on a later turn, you can hurl the flame at a creature within 30        feet of you. Make a ranged spell attack. On a hit, the target takes 1d8        fire damage.   If he casts the produce flame cantrip and holds it (i.e. doesn't attack or attempt to deal damage with it) would that still trigger this Flames of Plegethos ability?
98257
I am making an animation with a green background. When a lamp shines on my mesh, the background somehow makes the lamp shine on my mesh green as if the lamp was shining on it through green glass. How do I make this not happen? My mesh is opaque, has a diffuse BSDF, and is white. Thanks in advance.
55327
Let's say you have the ability to shine some light into a perfectly round sphere and the sphere's interior surface was perfectly smooth and reflective and there was no way for the light to escape.  If you could observe the inside of the sphere, what would you observe? A glow? And would temperature affect the outcome?  Seems silly, it's just something I've always thought about but never spent enough time (until now) to actually find an answer.