alt text t/m 48

book/demos/demo33/demo33.md

@@ -27,6 +27,7 @@ This demonstration is highly suitable for clarifying the paradox surrounding the
 ---
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+alt: a yellow flame made with Bunsen burner, shadow at the wall
 ---
 Scattering, emission, and resulting absorption are visible.
 ```
@@ -49,6 +50,7 @@ The setup is best built during the lesson. This to emphasize the sequence of eve
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+alt: the setup, left white screen, middle Bunsen burner, right sodium lamp.
 ---
 The setup: a sodium lamp, a blue flame, and a semi-translucent screen (a lab coat was used here).
 ```
@@ -70,6 +72,7 @@ The connection to the formation of the absorption spectrum in stellar atmosphere
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+alt: the shadow of the flame at the white screen
 ---
 The shadow on the other side of the screen.
 ```

book/demos/demo34/demo34.md

@@ -24,6 +24,7 @@
 width: 50%
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 name: demo34_fig4
+alt: various liquids stacked in a measuring cilinder. On top olive oil, below sunflower, water at the bottom.
 ---
 Various liquids stacked upon each other. Sunflower and olive oil have slightly different densities.
 ```
@@ -36,6 +37,7 @@ This demonstration can be performed as an introduction to or as practice with th
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 name: demo34_fig2
+alt: Various liquids stacked upon each other.
 ---
 Various liquids stacked upon each other.
 ```
@@ -91,6 +93,7 @@ Below are step-by-step instructions with tasks and questions that can be adjuste
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+alt: a teacher preparing the demo
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 An example of the demo
 ```
@@ -105,6 +108,7 @@ After just a few minutes, it is visible that the water changes color. This is be
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 name: demo34_fig3
+alt: A schematic of the various liquids and 'objects'
 ---
 A schematic of the various liquids and 'objects'
 ```

book/demos/demo35/demo35.md

@@ -49,6 +49,7 @@ Glue the tealight candle onto the lid of the jar. Screw the jar upside down on t
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+alt: Tealight candle in a closed jar.
 ---
 Tealight candle in a closed jar.
 ```

book/demos/demo36/demo36.md

@@ -53,6 +53,7 @@ This demonstration is earlier described in {cite:t}`Vonk2015`.
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+alt: the setup consisting of a heater with a flask on it, an aquarium filled with blue colored water, flask and water are connected with a tube
 ---
 The setup of the experiment.
 ```
@@ -93,6 +94,7 @@ When the Erlenmeyer flask is heated, the air inside it expands. This means you s
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+alt: the flask is fully filled with the blue colored water from the aquarium
 ---
 The flask is fully filled with water at the end of the demonstration. 
 ```

book/demos/demo37/demo37.ipynb

@@ -39,6 +39,7 @@
     "width: 70%\n",
     "align: center\n",
     "name: demo37_fig1\n",
+    "alt: the setup, a syringe connected to a pressure sensor.\n",
     "---\n",
     "The experimental setup, with a syringe and a pressure sensor.\n",
     "```\n",

book/demos/demo38/demo38.md

@@ -24,6 +24,7 @@
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 name: demo38_fig2
+alt: U-shaped tube, liquid at the left is lower than at the right
 ---
 U-tube after removal of the stopper.
 ```
@@ -61,6 +62,7 @@ Once it's clear what the class thinks, remove the stopper. The liquid level rise
 width: 70%
 align: center
 name: demo38_fig1
+alt: U shape tube with liquid and stopper, liquid left and right are at same level
 ---
 U-tube with liquid and stopper.
 ```

book/demos/demo39/demo39.md

@@ -23,6 +23,7 @@
 ---
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+alt: a fire tornado in a rotating trash can
 ---
 The fire tornado in a rotating trash can.
 ```
@@ -44,6 +45,7 @@ A rare and devastating phenomenon in forest fires in warm, dry areas is a fire t
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+alt: various items next to the trash bin
 ---
 Some items that can be useful if you want to investigate suggestions from students.
 ```
@@ -72,6 +74,7 @@ Explicitly invite them to come up with various suggestions how such a tornado co
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 name: demo39_fig3
+alt: a concept cartoon with various statements on the explanation of the fire tornado
 ---
 The concept cartoon can help elicit ideas. You can go two ways with the statements shown: *what question is behind a statement* and *what experiment can you come up with for it?* By the way, all these people are somehow right.
 ```

book/demos/demo40/demo40.md

@@ -45,6 +45,7 @@ This demonstration is meant to evoke fascination and amazement while simultaneou
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 name: demo40_fig1
+alt: a large can, an elastic band at the side can be seen
 ---
 This can comes back when rolled away.
 ```
@@ -58,6 +59,7 @@ This can comes back when rolled away.
 width: 50%
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 name: demo40_fig2
+alt: schematic of inside of the can
 ---
 Inside of the can: schematic.
 ```
@@ -89,6 +91,7 @@ Scientists are never entirely sure of their solutions. Your class can be sure of
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 align: center
 name: demo40_fig3
+alt: the schematic illustrating how torque provides the explanation of the can rolling back
 ---
 Explanation - torque explains the return.
 ```

book/demos/demo41/demo41.ipynb

@@ -28,6 +28,7 @@
     "```{figure} demo41_figure2.jpg\n",
     ":width: 90%\n",
     ":align: center\n",
+    ":alt: concept cartoon on students' predictions\n",
     "```\n",
     "\n",
     "## Introduction\n",
@@ -56,6 +57,7 @@
     "width: 90%\n",
     "align: center\n",
     "name: demo41_fig1\n",
+    "alt: three side by side pictures of the water level in the two bottles at various stages\n",
     "---\n",
     "The various stages of the demonstration.\\\n",
     "*left* The setup just before conducting the experiment.\\\n",

book/demos/demo42/demo42.md

@@ -24,6 +24,7 @@
 width: 70%
 align: center
 name: demo42_fig1
+alt: the setup, left a soda can wrapped in water paper, right without. In both can a thermometer is inserted
 ---
 The two cans contain hot water (same initial temperature) and a temperature sensor. The temperature measurements are displayed on a digital board. Which one cools faster? 
 ```
@@ -63,6 +64,7 @@ Ensure that hot water is available, as well as a handkerchief that can be soaked
 width: 80%
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 name: demo42_fig2
+alt: two graphs of temperature in single diagram clearly showing the wrapped can cools faster
 ---
 We immediately see the difference in cooling between the two cans. The can with the wet handkerchief (green) cools much faster than the can without.
 ```

book/demos/demo43/demo43.md

@@ -45,6 +45,7 @@ How can you experience force and motion in person without too much interference
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 name: demo43_fig2
+alt: a bowling ball near a cone, teacher with broom in hand
 ---
 A track including a pole to experience how 'easy' it is to make turns.
 ```
@@ -63,6 +64,7 @@ Students can gain similar experiences with a heavily loaded supermarket cart. Th
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 name: demo43_fig1
+alt: large bowling ball
 ---
 As the ball is heavy, friction hardly plays a role allowing to investigate Newton's laws of motion.
 ```

book/demos/demo44/demo44.md

@@ -56,6 +56,7 @@ Place a dropper, similar to the one used for pipetting, on the table. Position t
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 name: demo44_fig1
+alt: the setup, functiongenerator connected to LED strip, water dropper at front.
 ---
 The setup.
 ```

book/demos/demo45/demo45.md

@@ -24,6 +24,7 @@
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 name: demo45_fig1
+alt: the setup, three weights attached to wire connected to a spring scale, and further connected to a pole
 ---
 The basic setup.
 ```
@@ -53,6 +54,7 @@ Replace the stand with the equivalent mass blocks, as shown in {numref}`Figure {
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 name: demo45_fig2
+alt: same setup except pole is replace by string through pulley with weights attached
 ---
 The modified setup; the result is the same.
 ```

book/demos/demo46/demo46.md

@@ -24,6 +24,7 @@
 width: 80%
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 name: demo46_fig2
+alt: parabolic orbit illustrated by water dropplets 
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 Ticker (height 2.4 cm, frequency 100 drops/s) and parabola of drops.
 ```
@@ -63,6 +64,7 @@ Stroboscopic lighting can trigger seizures in people with certain kinds of epile
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 name: demo46_fig1
+alt: schematic setup
 ---
 The setup.
 ```
@@ -88,6 +90,7 @@ Your demonstration might proceed as follows, starting from when the audience see
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 name: demo46_fig3
+alt: picture of water dropplets and parabolic orbit with small horizontal velocity of water dropplets.
 ---
 Small initial speed.
 ```
@@ -101,6 +104,7 @@ Small initial speed.
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 name: demo46_fig4
+alt: picture of water dropplets and parabolic orbit with larger horizontal velocity of water dropplets.
 ---
 Large initial speed.
 ```

book/demos/demo47/demo47.md

@@ -33,6 +33,7 @@ Students are taught about charge and electric fields. In demonstrations, teacher
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 name: demo47_fig2
+alt: cloth, pvc tube and charge sensor
 ---
 The charge sensor, plastic rods, and a cloth used to charge the objects by rubbing.
 ```

book/demos/demo48/demo48.md

@@ -29,6 +29,7 @@ This demonstration shows the alternating voltage across a (incandescent-bicycle)
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+alt: the setup with light bulbs in series and a voltage meter
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 The setup includes a voltage sensor (range -10 to 10 V) and a luminosity sensor.
 ```
@@ -46,6 +47,7 @@ The setup includes a voltage sensor (range -10 to 10 V) and a luminosity sensor.
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 name: demo48_fig3
+alt: a setup with a incandescent lamp and a photodiode
 ---
 Optionally one can do measurement on a fluorescent light.
 ```
@@ -62,6 +64,7 @@ Secure the luminosity sensor in a stand to keep it at the correct height above t
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 name: demo48_fig2
+alt: the graphs in one diagram showing the applied and measured voltage. Frequency of measured voltage across light is twice as high.
 ---
 Two measurements in one diagram: the alternating voltage across the lamp and the luminosity of the lamp over time.
 ```
@@ -82,6 +85,7 @@ Two measurements in one diagram: the alternating voltage across the lamp and the
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 name: demo48_fig4
+alt: oscilloscope showing the actual measurement
 ---
 Why is the measured frequency 100 Hz?
 ```