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Join the ServerThe tiered classroom of the Royal Academy of Magic.
Sunlight slanted through the tall arched windows, illuminating the fine dust floating in the air.
Lia stood on the podium, the chalk in her hand leaving the final line of equations on the blackboard.
The sound of the chalk snapping was crisp and loud.
She patted the white dust from her hands and turned to look at the audience.
The seats were not full.
Ever since her performance at the Mages’ Association shattered the mental equilibrium of three Eighth-Circle mages, the number of students attending her lectures had noticeably decreased.
In particular, low-level apprentices with poor psychological resilience had been strictly forbidden by their mentors from approaching this classroom.
However, this did not prevent the remaining audience from being of extremely high quality.
The first few rows were occupied almost entirely by formal mages of the Fifth Circle and above, with several professors in dark robes mixed among them.
“That concludes today’s application of calculus.”
Lia tossed the half-piece of chalk back into the box.
The sound of parchment being packed and quills being put away rustled through the room.
“Wait a moment.”
Lia’s voice traveled clearly through every corner of the classroom via the amplification array.
The sound of packing stopped.
Everyone looked up at her.
“We have a little time left, so let’s talk about a recent discovery.”
Lia picked up the eraser and wiped away half the blackboard’s formulas, leaving a blank space.
In that space, she wrote a name.
Hertz.
“The Alchemy Association has been playing with electric sparks lately.”
Lia drew a simple circuit diagram on the blackboard: a zinc plate, an electroscope, and arrows representing rays of light.
“Mr. Hertz discovered that when ultraviolet light shines on a negatively charged zinc plate, the metal foil of the electroscope closes.”
“This means the charge has been lost.”
“Or, to put it more intuitively, the light knocked electrons out of the metal.”
The mages below reacted indifferently.
This wasn’t particularly big news; The Truth Daily had published this experiment half a month ago.
Many mages of the Thermodynamics school believed this was a thermal effect of light—the light heated the metal, giving the electrons enough energy to jump out.
It was a reasonable assumption.
Lia looked at the “matter-of-fact” expressions below.
“The interesting part is this.”
Lia drew a checkmark next to “Ultraviolet Light” and then wrote “Red Light” below it, marking it with a cross.
“If you illuminate it with red light, no matter how high you turn the intensity—even if the zinc plate becomes hot to the touch—the foil of the electroscope does not budge.”
“Yet with ultraviolet light, even if it is just a faint glimmer, the foil closes immediately.”
The air in the classroom seemed to freeze for a second.
Several previously indifferent professors sat up straight, beginning to anticipate what insight Lia might offer.
“If it were a thermal effect, the greater the intensity and the higher the energy, the more the electrons should emerge.”
“The total energy of high-intensity red light is certainly higher than that of faint ultraviolet light.”
“So why can’t red light knock out electrons?”
“This does not conform to wave theory.”
Lia set down the eraser.
“According to wave theory, the energy of a light wave depends on its amplitude—its brightness.”
“As long as the brightness is high enough, red light should also be able to shake the electrons out.”
“But the fact is, it cannot.”
Lia propped both hands on the podium, her gaze sweeping across the front row.
“Who can explain this?”
No one spoke.
Only the sound of a quill dropping to the floor could be heard.
It was a dead end.
Existing optical theory had hit a wall here.
A middle-aged man in gray robes stood up.
Pinned to his chest was a Seventh-Circle mage badge, the high-level certification for the School of Optics.
Bernard.
A famous master of optics theory in the capital and a staunch supporter of the wave theory.
Bernard’s expression was not pleasant.
“Professor Lia.”
His voice was somewhat raspy, like coarse sandpaper rubbing together.
“I have also replicated this experiment.”
“It isn’t just red and violet light; if you vary the frequency of the light, there is a threshold value.”
“For light below this frequency, no matter how long you shine it or how bright it is, no electrons escape.”
“For light above this frequency, they escape as soon as the light hits, and the kinetic energy of the escaping electrons is only related to the frequency, not the brightness.”
Bernard stared fixedly at the circuit diagram on the blackboard.
“This completely contradicts the light wave energy theory derived from Maxwell’s Equations.”
“As an Honorary Professor of the Physics Department and the person who unified electromagnetic theory…”
“What is your view?”
The gaze of the entire hall instantly focused on Lia.
The Optics faction was currently being driven mad by this experiment.
They desperately needed an explanation, even if that explanation would overturn their previous understanding.
Lia looked at Bernard.
Her fingers tapped lightly against the edge of the podium.
She was thinking.
Though the answer was in her head, she couldn’t just blurt it out.
That would arouse suspicion.
Furthermore, she needed to let it ferment.
She needed to let this bullet fly in the air for a while.
“I have a few conjectures.”
Lia stopped tapping.
She picked up the thick lesson plan and tucked it under her arm.
“But I need to verify the mathematical self-consistency.”
She looked at Bernard, then at the eager eyes in the audience.
“The day after tomorrow.”
“In the public lecture the day after tomorrow, I will speak specifically on this.”
“I will discuss my understanding of the photoelectric effect.”
Having said that.
Lia turned and walked down the podium, her black mage robes billowing behind her.
“Class dismissed.”
***
Two days passed quickly.
But for the mages of the capital, it felt like years.
The news that Lia was going to tackle the photoelectric effect spread throughout the entire magical district.
The Optics faction, the Thermodynamics faction, the Electromagnetics faction…
Even the Necromancy faction, which usually stayed out of everything, sent representatives.
On the morning of the third day.
The Royal Academy of Magic’s First Teaching Building.
Not only were the seats full this morning.
Even the aisles were packed with high-level mages clutching notebooks.
The air was permeated with the scent of anxiety.
Various mana fluctuations collided in the cramped space, emitting the crackling sound of static electricity.
When Lia entered the classroom, she felt as if she were walking into a pressure cooker.
Hundreds of pairs of eyes turned toward her simultaneously.
Klein was at her side, wordlessly expanding a barrier to isolate those over-eager gazes.
Lia walked up to the podium.
She picked up a piece of chalk and wrote a formula directly in the center of the blackboard.
E=hνIt was the formula she had previously proposed to explain blackbody radiation.
A commotion rose from the audience.
“This again?”
“Isn’t that Planck’s formula for calculating energy quanta?”
“Could light also be…”
Lia turned around.
The chalk tapped against the formula.
“A few days ago, someone asked me how to explain the photoelectric effect.”
“Why does the energy of light seem only related to frequency and not to intensity?”
“Why does light wave theory fail here?”
Lia’s voice was calm and cold.
“Because our understanding of light has been missing a half from the very beginning.”
Beside the formula, she drew a wavy line.
Then she took the eraser and wiped away half of the wavy line.
In the remaining blank space, she drew a small, solid dot.
“If.”
“I mean, if.”
“Light, during its propagation and absorption, does not spread continuously like a water wave.”
“But instead, acts like this chalk dust.”
Lia crushed a small piece of chalk.
The white dust drifted down in the sunlight, the particles distinct.
“It exists in discrete grains.”
BOOM!
The classroom exploded in noise.
Though they had premonitions, and though the concept of “energy quanta” had been laid out as a foundation before.
When Lia personally spoke the words “light is in grains,” the impact was still immense.
Bernard sat in the first row.
His hand shook, and ink spread into a black stain on his notebook.
“Particle theory?”
Bernard stood up, his voice rising.
“You want to promote the corpuscular theory? That’s impossible! How do you explain interference fringes? How do you explain the bright spot?”
“Those experiments were enough to nail the corpuscular theory into its coffin for a hundred years!”
“Sit down.”
Lia uttered the two words coldly.
Klein took a step forward.
The pressure of an Eighth-Circle mage was released just slightly.
Bernard grit his teeth and sat back down.
“I did not say it was the corpuscle those people spoke of.”
Lia continued writing on the blackboard.
“I call it—the Light Quantum.”
“Or,”
“The Photon.”
She wrote the word next to the small dot.
“Let us look at the world from a different angle.”
She then turned to face the entire class.
She was about to provide a perfect exposition of her theory to the entire world.
“View light as a large number of bullets fired from a staff.”
“The energy of each bullet is determined by its frequency.”
Lia pointed at the formula.
“Violet light has a high frequency, so violet light bullets have high energy.”
“Red light has a low frequency, so red light bullets have low energy.”
On one side of the blackboard, she drew a schematic of a metal surface.
“An electron is bound within the interior of the metal.”
“To escape, the electron needs to pay a ‘ransom’.”
“I call it the work function, denoted as W, Lia wrote ‘W’ next to the electron.
“This is a one-on-one collision.”
Lia made a striking gesture in the air.
“One photon hits one electron.”
“If the energy E of this photon is less than the ransom W. The electron eats the photon, wobbles a bit, finds it doesn’t have enough money to buy its freedom, and stays inside the metal.”
“No matter how many of these red light bullets you fire.”
“Even if you turn the intensity to infinity and fire a hundred million, or a billion bullets.”
“Each individual bullet lacks sufficient energy.”
“For every individual electron, it will always face a failed transaction.”
“Therefore, red light cannot knock out electrons.”
The hall grew quiet.
The noisy discussions gradually vanished.
Every mage was following Lia’s logic.
Simple.
It was outrageously simple, yet it perfectly explained the problem that had plagued everyone for years.
Lia continued.
“If you use violet light.”
“The energy E of a violet light bullet is greater than W.”
“One bullet hits.”
“The electron receives enough energy, pays the ransom W, and the remaining energy becomes the travel fare for its escape.”
Lia wrote the equation on the blackboard that was destined to be recorded in history.
Ek=hν−W“Ekis the maximum kinetic energy of the escaping electron. hνis the energy of the photon.”
“Wis the work function.”
Lia tossed the chalk aside.
She patted her hands.
“What does intensity represent?”
“Intensity only represents the number of photons.”
“The stronger the violet light, the more photons there are, and the more electrons will be knocked out.”
“But the speed at which each electron escapes is only related to the frequency.”
Lia looked at the audience.
“This is, in my view, the entire secret of the photoelectric effect.”
A deathly silence filled the classroom.
A long time passed.
Bernard raised his hand tremblingly.
“But…”
His voice carried a hint of disbelief.
“If light is a particle…”
“Then what are those interference fringes we observed before?”
“When two beams of light meet, they create alternating light and dark patterns.”
“That is a characteristic of waves.”
“How could particles cancel each other out?”
“Could two photons colliding simply vanish into thin air?”
“Could it be that you, Miss Lia, are also a member of the corpuscular theory?!”
Bernard’s aura surged alongside his words.
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Read : Oh No, The Girl I Possessed Has Come Knocking On my Door!
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