Morötesi ışık duvardaki kodu gösterdi.

Morötesi means ultraviolet.

It is built from:

• mor = purple / violet
• ötesi = beyond, the other side of

So the literal idea is beyond violet.

In modern Turkish, morötesi is commonly written as one word when it means ultraviolet. In this sentence, it works like an adjective before ışık.

Turkish normally puts adjectives before the noun they describe.

So:

• morötesi ışık = ultraviolet light

This is the normal Turkish pattern:

• adjective + noun

Just like:

• büyük ev = big house
• mavi araba = blue car

Turkish does not have articles like English a/an and the.

That means a noun like ışık can be understood as:

• light
• a light
• the light

The exact meaning depends on context. In a full sentence, Turkish often leaves definiteness to context instead of using a separate article.

Duvardaki means something like the one on the wall or that is on the wall.

It breaks down like this:

• duvar = wall
• duvarda = on the wall
• duvardaki = the one that is on the wall / on-the-wall

The suffix -ki turns a location phrase into something that can describe a noun.

So:

• duvardaki kod = the code on the wall
• more literally: the code that is on the wall

This is a very common Turkish structure.

Because kodu is the definite/specific direct object form.

Turkish often marks a specific direct object with the accusative suffix:

• kod = code
• kodu = the code / that code, as the object of the verb

Here, the sentence is talking about a specific code, so kodu is natural.

The suffix is the accusative -(y)I, which changes by vowel harmony. Since kod has the vowel o, the suffix appears as -u:

• kod + u = kodu

A useful comparison:

• Kod gösterdi would sound more like showed a code / showed code and is less natural here.
• Kodu gösterdi = showed the code

In isolation, kodu can sometimes look like the 3rd person possessive form, meaning his/her/its code.

But in this sentence, it is understood as the accusative object:

• duvardaki kodu gösterdi = showed the code on the wall

Why? Because gösterdi needs an object here, and kodu fits that role perfectly.

If Turkish wanted to say his/her code as a direct object, it would usually be:

• kodunu

So in this sentence, kodu is best understood as the code in the accusative.

Gösterdi comes from the verb göstermek, which means to show.

Breakdown:

• göster- = show
• -di = past tense

So gösterdi means:

• showed
• in context, possibly revealed

It is 3rd person singular:

• o gösterdi = he/she/it showed

Turkish does not need a separate word for it here, because the verb form and context are enough.

Because Turkish often uses Subject–Object–Verb order as its neutral word order.

This sentence is:

• Morötesi ışık = subject
• duvardaki kodu = object
• gösterdi = verb

So the structure is:

• Ultraviolet light
  • the code on the wall
    • showed/revealed

English usually prefers the verb earlier:

• The ultraviolet light revealed the code on the wall.

Turkish usually puts the verb last.

A helpful breakdown is:

• morötesi = ultraviolet
• ışık = light
• duvardaki = on-the-wall / that is on the wall
• kodu = the code (object form)
• gösterdi = showed / revealed

So the structure is literally close to:

• Ultraviolet light the-on-the-wall code showed

A more natural English version is:

• The ultraviolet light revealed the code on the wall.

These letters are often tricky for English speakers:

• ı = a dotless i. It does not sound like English ee. It is a short, central/back vowel with no exact English equivalent.
• ş = sh
• ö = like the vowel in German schön or French peu; there is no exact standard English equivalent

So roughly:

• ışık sounds something like uh-shuk, but that is only an approximation
• morötesi has an ö sound that English speakers usually need practice with

The spelling in Turkish is very regular, so once you learn the sounds of the letters, pronunciation becomes much easier.