Single-slit diffraction minima angle
For order 1, a 500 nm wavelength and a 0.1 mm slit, the minimum sits at 0.286480091241°, where the sine of the angle is 0.005. Use it to prepare answer keys or check a laser lab before measuring. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Order
- 1
- Wavelength
- 0.0000005
- Slit width
- 0.0001
- Angle degrees
- 0.2864800912 degrees
- Angle radians
- 0.0050000208
- Sin theta
- 0.005
- Max order
- 199
When monochromatic light passes a single narrow slit, the far-field pattern shows a bright central maximum flanked by dark minima at discrete angles.
The sine condition for single-slit diffraction minima
Illumination of a long rectangular aperture of width a by a plane wave of wavelength lambda produces, in the Fraunhofer far field or in the focal plane of a collecting lens, a diffraction envelope whose intensity minima sit where secondary wavelets across the slit cancel. The standard destructive-interference condition is a times sine of the angle theta measured from the optical axis equals an integer order m times the wavelength. Rearrangement gives the angular position theta equals the inverse sine of the ratio m lambda over a.
The order m must be a nonzero integer: positive values place minima on one side of the central peak and negative values place the symmetric partners on the other side. Order zero is the central maximum, not a dark fringe, so this calculator never accepts m equals zero. Because the absolute value of sine cannot exceed one, only orders with absolute m lambda over a less than or equal to one are physically observable; higher orders simply do not appear for that aperture and wavelength.
Wider slits pack minima closer to the axis; narrower slits or longer wavelengths spread the pattern.
Where a minima-angle calculator earns its keep
Secondary-school and college optics courses assign far-field pattern problems that ask for the angle of the first dark fringe, the second minimum, or the half-width of the central peak derived from order one; a single trusted oracle that returns degrees and radians speeds grading and demo setup. Teaching labs that measure laser wavelength from measured fringe angles need a forward calculator that matches the same a sine theta equals m lambda relation used in the experiment write-up before students invert for lambda.
Instrument design sketches for monochromators and entrance slits estimate how wide a diffraction envelope will be at a given wavelength before more detailed wave-optics models are run. Content sites that rank for single slit diffraction minima angle calculator benefit from a live tool whose free browser path matches the paid automation path byte-for-byte on the same pure module.
Keep lengths in one unit system, pin rounded angles in tests, and you get reproducible minima angles for homework, LMS plugins, and edge workers without standing up a full wave-optics stack of your own.
What you can do with it
Homework and lab answer keys
Compute the angular position of the m-th single-slit minimum from textbook order, wavelength, and slit width so teachers and auto-graders share one ground truth.
Laser wavelength teaching labs
Forward-check measured dark-fringe angles against a·sin(θ)=m·λ for a known slit before solving for λ from the inverse experiment.
Slit and monochromator envelope estimates
Estimate how far the first few diffraction minima sit from the optical axis when sizing entrance slits at a design wavelength.
FAQ
What formula does this single-slit minima angle calculator use?
The standard condition for single-slit minima: a·sin(θ) = m·λ, so θ = arcsin(m·λ/a). Slit width and wavelength must use the same length unit; m is a nonzero integer order.
What happens if the slit width is zero?
Zero (or non-positive) slit width would make the formula divide by zero, so it is rejected with a clear validation error and is not charged.
What if |m·λ/a| is greater than one?
There is no real angle for that order with the given aperture and wavelength.
What is the angle of the first minimum for a 0.1 mm slit and 500 nm light?
It is 0.286480091241°, or 0.00500002083357 radians. The sine of that angle is 0.005, the wavelength divided by the slit width.
Does a wider slit spread the minima apart?
No, the opposite happens. A wider slit or a shorter wavelength pulls the minima closer to the centre, while a narrower slit or a longer wavelength spreads them out.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/optics/single-slit-minima-angle \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"order":1,"wavelength":5e-7,"slit_width":0.0001}'const res = await fetch("https://api.kit.forhosting.com/optics/single-slit-minima-angle", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"order": 1,
"wavelength": 5e-7,
"slit_width": 0.0001
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/optics/single-slit-minima-angle",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"order": 1,
"wavelength": 5e-7,
"slit_width": 0.0001
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/optics/single-slit-minima-angle", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"order":1,"wavelength":5e-7,"slit_width":0.0001}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"order":1,"wavelength":5e-7,"slit_width":0.0001}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/optics/single-slit-minima-angle", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"order": 1,
"wavelength": 5e-7,
"slit_width": 0.0001
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "optics.single_slit_minima_angle",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
The angular position of those minima follows the sine relation slit width times sine of theta equals order times wavelength: a sin θ equals m λ, so θ equals arcsin of m λ over a. This capability takes the integer order, the wavelength, and the slit width in matching length units and returns that angle in degrees and radians. Non-positive aperture or wavelength, zero or fractional order, and orders whose sine argument exceeds one are rejected with invalid_input rather than a silent empty success. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.
The sine condition for single-slit diffraction minima
This endpoint evaluates only that closed-form angular condition. It does not integrate the full single-slit intensity envelope sin beta over beta squared, does not treat circular apertures or Airy disks, and does not compute double-slit fringe spacing or grating resolving power. The pipeline is pure floating-point arithmetic with no network calls, no random seeds, and no wall-clock timestamps, so identical order, wavelength, and slit width always produce identical JSON.
Request fields, response shape, and validation failures
Zero slit width is called out explicitly because dividing by a would be undefined. Wire the free browser form for homework and lab demos, then call the identical contract from scripts when you need bulk answer keys. POST a JSON object with three required fields: order, the nonzero integer m of the minimum; wavelength, lambda in the same length unit as the aperture; and slit_width, the aperture width a. Aliases such as m, n, or min_order for the order, lambda, wave_length, or wl for the wavelength, and a, width, slit, or slitWidth for the aperture are accepted so scripts written in textbook notation do not need a rename layer. Missing fields, non-numeric strings, NaN, Infinity, non-positive slit width, non-positive wavelength, zero or non-integer order, and orders with absolute m lambda over a greater than one fail with invalid_input and are not charged. On success the response echoes cleaned order, wavelength, and slit_width, returns angle_degrees and angle_radians for display and further trigonometry, includes sin_theta equal to m lambda over a for intermediate checks, reports max_order as the largest positive integer order that still has a real angle for the given a over lambda, and adds formula and unit strings. Classic checks include order one with a equals one times ten to the minus four metres and lambda equals five times ten to the minus seven metres, which yields a small angle near zero point two nine degrees; the same geometry with order zero as the explicit central-maximum error path; and a zero slit width as the mandatory invalid_input path for division by zero. Successful API calls use prepaid KIT balance at the published base of $0.002 per item.
Where a minima-angle calculator earns its keep
Because this capability is a pure parse engine, every successful call costs the published base of $0.002 with no model tokens and no outbound network, and failed validation does not consume balance.
Technical questions
Why is order m = 0 rejected?
m = 0 corresponds to the central maximum of the single-slit pattern, not a dark minimum. Only m = ±1, ±2, … label minima under the standard condition.
What does the single-slit minima angle calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.